Add google-endpoints to third_party/.

third_party/google-endpoints/future/backports/urllib/request.py

Index: third_party/google-endpoints/future/backports/urllib/request.py
diff --git a/third_party/google-endpoints/future/backports/urllib/request.py b/third_party/google-endpoints/future/backports/urllib/request.py
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index 0000000000000000000000000000000000000000..b1545ca0f5d55c1689a71b4dda1389080bb9bbe0
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+"""
+Ported using Python-Future from the Python 3.3 standard library.
+
+An extensible library for opening URLs using a variety of protocols
+
+The simplest way to use this module is to call the urlopen function,
+which accepts a string containing a URL or a Request object (described
+below).  It opens the URL and returns the results as file-like
+object; the returned object has some extra methods described below.
+
+The OpenerDirector manages a collection of Handler objects that do
+all the actual work.  Each Handler implements a particular protocol or
+option.  The OpenerDirector is a composite object that invokes the
+Handlers needed to open the requested URL.  For example, the
+HTTPHandler performs HTTP GET and POST requests and deals with
+non-error returns.  The HTTPRedirectHandler automatically deals with
+HTTP 301, 302, 303 and 307 redirect errors, and the HTTPDigestAuthHandler
+deals with digest authentication.
+
+urlopen(url, data=None) -- Basic usage is the same as original
+urllib.  pass the url and optionally data to post to an HTTP URL, and
+get a file-like object back.  One difference is that you can also pass
+a Request instance instead of URL.  Raises a URLError (subclass of
+IOError); for HTTP errors, raises an HTTPError, which can also be
+treated as a valid response.
+
+build_opener -- Function that creates a new OpenerDirector instance.
+Will install the default handlers.  Accepts one or more Handlers as
+arguments, either instances or Handler classes that it will
+instantiate.  If one of the argument is a subclass of the default
+handler, the argument will be installed instead of the default.
+
+install_opener -- Installs a new opener as the default opener.
+
+objects of interest:
+
+OpenerDirector -- Sets up the User Agent as the Python-urllib client and manages
+the Handler classes, while dealing with requests and responses.
+
+Request -- An object that encapsulates the state of a request.  The
+state can be as simple as the URL.  It can also include extra HTTP
+headers, e.g. a User-Agent.
+
+BaseHandler --
+
+internals:
+BaseHandler and parent
+_call_chain conventions
+
+Example usage:
+
+import urllib.request
+
+# set up authentication info
+authinfo = urllib.request.HTTPBasicAuthHandler()
+authinfo.add_password(realm='PDQ Application',
+                      uri='https://mahler:8092/site-updates.py',
+                      user='klem',
+                      passwd='geheim$parole')
+
+proxy_support = urllib.request.ProxyHandler({"http" : "http://ahad-haam:3128"})
+
+# build a new opener that adds authentication and caching FTP handlers
+opener = urllib.request.build_opener(proxy_support, authinfo,
+                                     urllib.request.CacheFTPHandler)
+
+# install it
+urllib.request.install_opener(opener)
+
+f = urllib.request.urlopen('http://www.python.org/')
+"""
+
+# XXX issues:
+# If an authentication error handler that tries to perform
+# authentication for some reason but fails, how should the error be
+# signalled?  The client needs to know the HTTP error code.  But if
+# the handler knows that the problem was, e.g., that it didn't know
+# that hash algo that requested in the challenge, it would be good to
+# pass that information along to the client, too.
+# ftp errors aren't handled cleanly
+# check digest against correct (i.e. non-apache) implementation
+
+# Possible extensions:
+# complex proxies  XXX not sure what exactly was meant by this
+# abstract factory for opener
+
+from __future__ import absolute_import, division, print_function, unicode_literals
+from future.builtins import bytes, dict, filter, input, int, map, open, str
+from future.utils import PY2, PY3, raise_with_traceback
+
+import base64
+import bisect
+import hashlib
+import array
+
+from future.backports import email
+from future.backports.http import client as http_client
+from .error import URLError, HTTPError, ContentTooShortError
+from .parse import (
+    urlparse, urlsplit, urljoin, unwrap, quote, unquote,
+    splittype, splithost, splitport, splituser, splitpasswd,
+    splitattr, splitquery, splitvalue, splittag, to_bytes, urlunparse)
+from .response import addinfourl, addclosehook
+
+import io
+import os
+import posixpath
+import re
+import socket
+import sys
+import time
+import collections
+import tempfile
+import contextlib
+import warnings
+
+# check for SSL
+try:
+    import ssl
+    # Not available in the SSL module in Py2:
+    from ssl import SSLContext
+except ImportError:
+    _have_ssl = False
+else:
+    _have_ssl = True
+
+__all__ = [
+    # Classes
+    'Request', 'OpenerDirector', 'BaseHandler', 'HTTPDefaultErrorHandler',
+    'HTTPRedirectHandler', 'HTTPCookieProcessor', 'ProxyHandler',
+    'HTTPPasswordMgr', 'HTTPPasswordMgrWithDefaultRealm',
+    'AbstractBasicAuthHandler', 'HTTPBasicAuthHandler', 'ProxyBasicAuthHandler',
+    'AbstractDigestAuthHandler', 'HTTPDigestAuthHandler', 'ProxyDigestAuthHandler',
+    'HTTPHandler', 'FileHandler', 'FTPHandler', 'CacheFTPHandler',
+    'UnknownHandler', 'HTTPErrorProcessor',
+    # Functions
+    'urlopen', 'install_opener', 'build_opener',
+    'pathname2url', 'url2pathname', 'getproxies',
+    # Legacy interface
+    'urlretrieve', 'urlcleanup', 'URLopener', 'FancyURLopener',
+]
+
+# used in User-Agent header sent
+__version__ = sys.version[:3]
+
+_opener = None
+def urlopen(url, data=None, timeout=socket._GLOBAL_DEFAULT_TIMEOUT, **_3to2kwargs):
+    if 'cadefault' in _3to2kwargs: cadefault = _3to2kwargs['cadefault']; del _3to2kwargs['cadefault']
+    else: cadefault = False
+    if 'capath' in _3to2kwargs: capath = _3to2kwargs['capath']; del _3to2kwargs['capath']
+    else: capath = None
+    if 'cafile' in _3to2kwargs: cafile = _3to2kwargs['cafile']; del _3to2kwargs['cafile']
+    else: cafile = None
+    global _opener
+    if cafile or capath or cadefault:
+        if not _have_ssl:
+            raise ValueError('SSL support not available')
+        context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+        context.options |= ssl.OP_NO_SSLv2
+        context.verify_mode = ssl.CERT_REQUIRED
+        if cafile or capath:
+            context.load_verify_locations(cafile, capath)
+        else:
+            context.set_default_verify_paths()
+        https_handler = HTTPSHandler(context=context, check_hostname=True)
+        opener = build_opener(https_handler)
+    elif _opener is None:
+        _opener = opener = build_opener()
+    else:
+        opener = _opener
+    return opener.open(url, data, timeout)
+
+def install_opener(opener):
+    global _opener
+    _opener = opener
+
+_url_tempfiles = []
+def urlretrieve(url, filename=None, reporthook=None, data=None):
+    """
+    Retrieve a URL into a temporary location on disk.
+
+    Requires a URL argument. If a filename is passed, it is used as
+    the temporary file location. The reporthook argument should be
+    a callable that accepts a block number, a read size, and the
+    total file size of the URL target. The data argument should be
+    valid URL encoded data.
+
+    If a filename is passed and the URL points to a local resource,
+    the result is a copy from local file to new file.
+
+    Returns a tuple containing the path to the newly created
+    data file as well as the resulting HTTPMessage object.
+    """
+    url_type, path = splittype(url)
+
+    with contextlib.closing(urlopen(url, data)) as fp:
+        headers = fp.info()
+
+        # Just return the local path and the "headers" for file://
+        # URLs. No sense in performing a copy unless requested.
+        if url_type == "file" and not filename:
+            return os.path.normpath(path), headers
+
+        # Handle temporary file setup.
+        if filename:
+            tfp = open(filename, 'wb')
+        else:
+            tfp = tempfile.NamedTemporaryFile(delete=False)
+            filename = tfp.name
+            _url_tempfiles.append(filename)
+
+        with tfp:
+            result = filename, headers
+            bs = 1024*8
+            size = -1
+            read = 0
+            blocknum = 0
+            if "content-length" in headers:
+                size = int(headers["Content-Length"])
+
+            if reporthook:
+                reporthook(blocknum, bs, size)
+
+            while True:
+                block = fp.read(bs)
+                if not block:
+                    break
+                read += len(block)
+                tfp.write(block)
+                blocknum += 1
+                if reporthook:
+                    reporthook(blocknum, bs, size)
+
+    if size >= 0 and read < size:
+        raise ContentTooShortError(
+            "retrieval incomplete: got only %i out of %i bytes"
+            % (read, size), result)
+
+    return result
+
+def urlcleanup():
+    for temp_file in _url_tempfiles:
+        try:
+            os.unlink(temp_file)
+        except EnvironmentError:
+            pass
+
+    del _url_tempfiles[:]
+    global _opener
+    if _opener:
+        _opener = None
+
+if PY3:
+    _cut_port_re = re.compile(r":\d+$", re.ASCII)
+else:
+    _cut_port_re = re.compile(r":\d+$")
+
+def request_host(request):
+
+    """Return request-host, as defined by RFC 2965.
+
+    Variation from RFC: returned value is lowercased, for convenient
+    comparison.
+
+    """
+    url = request.full_url
+    host = urlparse(url)[1]
+    if host == "":
+        host = request.get_header("Host", "")
+
+    # remove port, if present
+    host = _cut_port_re.sub("", host, 1)
+    return host.lower()
+
+class Request(object):
+
+    def __init__(self, url, data=None, headers={},
+                 origin_req_host=None, unverifiable=False,
+                 method=None):
+        # unwrap('<URL:type://host/path>') --> 'type://host/path'
+        self.full_url = unwrap(url)
+        self.full_url, self.fragment = splittag(self.full_url)
+        self.data = data
+        self.headers = {}
+        self._tunnel_host = None
+        for key, value in headers.items():
+            self.add_header(key, value)
+        self.unredirected_hdrs = {}
+        if origin_req_host is None:
+            origin_req_host = request_host(self)
+        self.origin_req_host = origin_req_host
+        self.unverifiable = unverifiable
+        self.method = method
+        self._parse()
+
+    def _parse(self):
+        self.type, rest = splittype(self.full_url)
+        if self.type is None:
+            raise ValueError("unknown url type: %r" % self.full_url)
+        self.host, self.selector = splithost(rest)
+        if self.host:
+            self.host = unquote(self.host)
+
+    def get_method(self):
+        """Return a string indicating the HTTP request method."""
+        if self.method is not None:
+            return self.method
+        elif self.data is not None:
+            return "POST"
+        else:
+            return "GET"
+
+    def get_full_url(self):
+        if self.fragment:
+            return '%s#%s' % (self.full_url, self.fragment)
+        else:
+            return self.full_url
+
+    # Begin deprecated methods
+
+    def add_data(self, data):
+        msg = "Request.add_data method is deprecated."
+        warnings.warn(msg, DeprecationWarning, stacklevel=1)
+        self.data = data
+
+    def has_data(self):
+        msg = "Request.has_data method is deprecated."
+        warnings.warn(msg, DeprecationWarning, stacklevel=1)
+        return self.data is not None
+
+    def get_data(self):
+        msg = "Request.get_data method is deprecated."
+        warnings.warn(msg, DeprecationWarning, stacklevel=1)
+        return self.data
+
+    def get_type(self):
+        msg = "Request.get_type method is deprecated."
+        warnings.warn(msg, DeprecationWarning, stacklevel=1)
+        return self.type
+
+    def get_host(self):
+        msg = "Request.get_host method is deprecated."
+        warnings.warn(msg, DeprecationWarning, stacklevel=1)
+        return self.host
+
+    def get_selector(self):
+        msg = "Request.get_selector method is deprecated."
+        warnings.warn(msg, DeprecationWarning, stacklevel=1)
+        return self.selector
+
+    def is_unverifiable(self):
+        msg = "Request.is_unverifiable method is deprecated."
+        warnings.warn(msg, DeprecationWarning, stacklevel=1)
+        return self.unverifiable
+
+    def get_origin_req_host(self):
+        msg = "Request.get_origin_req_host method is deprecated."
+        warnings.warn(msg, DeprecationWarning, stacklevel=1)
+        return self.origin_req_host
+
+    # End deprecated methods
+
+    def set_proxy(self, host, type):
+        if self.type == 'https' and not self._tunnel_host:
+            self._tunnel_host = self.host
+        else:
+            self.type= type
+            self.selector = self.full_url
+        self.host = host
+
+    def has_proxy(self):
+        return self.selector == self.full_url
+
+    def add_header(self, key, val):
+        # useful for something like authentication
+        self.headers[key.capitalize()] = val
+
+    def add_unredirected_header(self, key, val):
+        # will not be added to a redirected request
+        self.unredirected_hdrs[key.capitalize()] = val
+
+    def has_header(self, header_name):
+        return (header_name in self.headers or
+                header_name in self.unredirected_hdrs)
+
+    def get_header(self, header_name, default=None):
+        return self.headers.get(
+            header_name,
+            self.unredirected_hdrs.get(header_name, default))
+
+    def header_items(self):
+        hdrs = self.unredirected_hdrs.copy()
+        hdrs.update(self.headers)
+        return list(hdrs.items())
+
+class OpenerDirector(object):
+    def __init__(self):
+        client_version = "Python-urllib/%s" % __version__
+        self.addheaders = [('User-agent', client_version)]
+        # self.handlers is retained only for backward compatibility
+        self.handlers = []
+        # manage the individual handlers
+        self.handle_open = {}
+        self.handle_error = {}
+        self.process_response = {}
+        self.process_request = {}
+
+    def add_handler(self, handler):
+        if not hasattr(handler, "add_parent"):
+            raise TypeError("expected BaseHandler instance, got %r" %
+                            type(handler))
+
+        added = False
+        for meth in dir(handler):
+            if meth in ["redirect_request", "do_open", "proxy_open"]:
+                # oops, coincidental match
+                continue
+
+            i = meth.find("_")
+            protocol = meth[:i]
+            condition = meth[i+1:]
+
+            if condition.startswith("error"):
+                j = condition.find("_") + i + 1
+                kind = meth[j+1:]
+                try:
+                    kind = int(kind)
+                except ValueError:
+                    pass
+                lookup = self.handle_error.get(protocol, {})
+                self.handle_error[protocol] = lookup
+            elif condition == "open":
+                kind = protocol
+                lookup = self.handle_open
+            elif condition == "response":
+                kind = protocol
+                lookup = self.process_response
+            elif condition == "request":
+                kind = protocol
+                lookup = self.process_request
+            else:
+                continue
+
+            handlers = lookup.setdefault(kind, [])
+            if handlers:
+                bisect.insort(handlers, handler)
+            else:
+                handlers.append(handler)
+            added = True
+
+        if added:
+            bisect.insort(self.handlers, handler)
+            handler.add_parent(self)
+
+    def close(self):
+        # Only exists for backwards compatibility.
+        pass
+
+    def _call_chain(self, chain, kind, meth_name, *args):
+        # Handlers raise an exception if no one else should try to handle
+        # the request, or return None if they can't but another handler
+        # could.  Otherwise, they return the response.
+        handlers = chain.get(kind, ())
+        for handler in handlers:
+            func = getattr(handler, meth_name)
+            result = func(*args)
+            if result is not None:
+                return result
+
+    def open(self, fullurl, data=None, timeout=socket._GLOBAL_DEFAULT_TIMEOUT):
+        """
+        Accept a URL or a Request object
+
+        Python-Future: if the URL is passed as a byte-string, decode it first.
+        """
+        if isinstance(fullurl, bytes):
+            fullurl = fullurl.decode()
+        if isinstance(fullurl, str):
+            req = Request(fullurl, data)
+        else:
+            req = fullurl
+            if data is not None:
+                req.data = data
+
+        req.timeout = timeout
+        protocol = req.type
+
+        # pre-process request
+        meth_name = protocol+"_request"
+        for processor in self.process_request.get(protocol, []):
+            meth = getattr(processor, meth_name)
+            req = meth(req)
+
+        response = self._open(req, data)
+
+        # post-process response
+        meth_name = protocol+"_response"
+        for processor in self.process_response.get(protocol, []):
+            meth = getattr(processor, meth_name)
+            response = meth(req, response)
+
+        return response
+
+    def _open(self, req, data=None):
+        result = self._call_chain(self.handle_open, 'default',
+                                  'default_open', req)
+        if result:
+            return result
+
+        protocol = req.type
+        result = self._call_chain(self.handle_open, protocol, protocol +
+                                  '_open', req)
+        if result:
+            return result
+
+        return self._call_chain(self.handle_open, 'unknown',
+                                'unknown_open', req)
+
+    def error(self, proto, *args):
+        if proto in ('http', 'https'):
+            # XXX http[s] protocols are special-cased
+            dict = self.handle_error['http'] # https is not different than http
+            proto = args[2]  # YUCK!
+            meth_name = 'http_error_%s' % proto
+            http_err = 1
+            orig_args = args
+        else:
+            dict = self.handle_error
+            meth_name = proto + '_error'
+            http_err = 0
+        args = (dict, proto, meth_name) + args
+        result = self._call_chain(*args)
+        if result:
+            return result
+
+        if http_err:
+            args = (dict, 'default', 'http_error_default') + orig_args
+            return self._call_chain(*args)
+
+# XXX probably also want an abstract factory that knows when it makes
+# sense to skip a superclass in favor of a subclass and when it might
+# make sense to include both
+
+def build_opener(*handlers):
+    """Create an opener object from a list of handlers.
+
+    The opener will use several default handlers, including support
+    for HTTP, FTP and when applicable HTTPS.
+
+    If any of the handlers passed as arguments are subclasses of the
+    default handlers, the default handlers will not be used.
+    """
+    def isclass(obj):
+        return isinstance(obj, type) or hasattr(obj, "__bases__")
+
+    opener = OpenerDirector()
+    default_classes = [ProxyHandler, UnknownHandler, HTTPHandler,
+                       HTTPDefaultErrorHandler, HTTPRedirectHandler,
+                       FTPHandler, FileHandler, HTTPErrorProcessor]
+    if hasattr(http_client, "HTTPSConnection"):
+        default_classes.append(HTTPSHandler)
+    skip = set()
+    for klass in default_classes:
+        for check in handlers:
+            if isclass(check):
+                if issubclass(check, klass):
+                    skip.add(klass)
+            elif isinstance(check, klass):
+                skip.add(klass)
+    for klass in skip:
+        default_classes.remove(klass)
+
+    for klass in default_classes:
+        opener.add_handler(klass())
+
+    for h in handlers:
+        if isclass(h):
+            h = h()
+        opener.add_handler(h)
+    return opener
+
+class BaseHandler(object):
+    handler_order = 500
+
+    def add_parent(self, parent):
+        self.parent = parent
+
+    def close(self):
+        # Only exists for backwards compatibility
+        pass
+
+    def __lt__(self, other):
+        if not hasattr(other, "handler_order"):
+            # Try to preserve the old behavior of having custom classes
+            # inserted after default ones (works only for custom user
+            # classes which are not aware of handler_order).
+            return True
+        return self.handler_order < other.handler_order
+
+
+class HTTPErrorProcessor(BaseHandler):
+    """Process HTTP error responses."""
+    handler_order = 1000  # after all other processing
+
+    def http_response(self, request, response):
+        code, msg, hdrs = response.code, response.msg, response.info()
+
+        # According to RFC 2616, "2xx" code indicates that the client's
+        # request was successfully received, understood, and accepted.
+        if not (200 <= code < 300):
+            response = self.parent.error(
+                'http', request, response, code, msg, hdrs)
+
+        return response
+
+    https_response = http_response
+
+class HTTPDefaultErrorHandler(BaseHandler):
+    def http_error_default(self, req, fp, code, msg, hdrs):
+        raise HTTPError(req.full_url, code, msg, hdrs, fp)
+
+class HTTPRedirectHandler(BaseHandler):
+    # maximum number of redirections to any single URL
+    # this is needed because of the state that cookies introduce
+    max_repeats = 4
+    # maximum total number of redirections (regardless of URL) before
+    # assuming we're in a loop
+    max_redirections = 10
+
+    def redirect_request(self, req, fp, code, msg, headers, newurl):
+        """Return a Request or None in response to a redirect.
+
+        This is called by the http_error_30x methods when a
+        redirection response is received.  If a redirection should
+        take place, return a new Request to allow http_error_30x to
+        perform the redirect.  Otherwise, raise HTTPError if no-one
+        else should try to handle this url.  Return None if you can't
+        but another Handler might.
+        """
+        m = req.get_method()
+        if (not (code in (301, 302, 303, 307) and m in ("GET", "HEAD")
+            or code in (301, 302, 303) and m == "POST")):
+            raise HTTPError(req.full_url, code, msg, headers, fp)
+
+        # Strictly (according to RFC 2616), 301 or 302 in response to
+        # a POST MUST NOT cause a redirection without confirmation
+        # from the user (of urllib.request, in this case).  In practice,
+        # essentially all clients do redirect in this case, so we do
+        # the same.
+        # be conciliant with URIs containing a space
+        newurl = newurl.replace(' ', '%20')
+        CONTENT_HEADERS = ("content-length", "content-type")
+        newheaders = dict((k, v) for k, v in req.headers.items()
+                          if k.lower() not in CONTENT_HEADERS)
+        return Request(newurl,
+                       headers=newheaders,
+                       origin_req_host=req.origin_req_host,
+                       unverifiable=True)
+
+    # Implementation note: To avoid the server sending us into an
+    # infinite loop, the request object needs to track what URLs we
+    # have already seen.  Do this by adding a handler-specific
+    # attribute to the Request object.
+    def http_error_302(self, req, fp, code, msg, headers):
+        # Some servers (incorrectly) return multiple Location headers
+        # (so probably same goes for URI).  Use first header.
+        if "location" in headers:
+            newurl = headers["location"]
+        elif "uri" in headers:
+            newurl = headers["uri"]
+        else:
+            return
+
+        # fix a possible malformed URL
+        urlparts = urlparse(newurl)
+
+        # For security reasons we don't allow redirection to anything other
+        # than http, https or ftp.
+
+        if urlparts.scheme not in ('http', 'https', 'ftp', ''):
+            raise HTTPError(
+                newurl, code,
+                "%s - Redirection to url '%s' is not allowed" % (msg, newurl),
+                headers, fp)
+
+        if not urlparts.path:
+            urlparts = list(urlparts)
+            urlparts[2] = "/"
+        newurl = urlunparse(urlparts)
+
+        newurl = urljoin(req.full_url, newurl)
+
+        # XXX Probably want to forget about the state of the current
+        # request, although that might interact poorly with other
+        # handlers that also use handler-specific request attributes
+        new = self.redirect_request(req, fp, code, msg, headers, newurl)
+        if new is None:
+            return
+
+        # loop detection
+        # .redirect_dict has a key url if url was previously visited.
+        if hasattr(req, 'redirect_dict'):
+            visited = new.redirect_dict = req.redirect_dict
+            if (visited.get(newurl, 0) >= self.max_repeats or
+                len(visited) >= self.max_redirections):
+                raise HTTPError(req.full_url, code,
+                                self.inf_msg + msg, headers, fp)
+        else:
+            visited = new.redirect_dict = req.redirect_dict = {}
+        visited[newurl] = visited.get(newurl, 0) + 1
+
+        # Don't close the fp until we are sure that we won't use it
+        # with HTTPError.
+        fp.read()
+        fp.close()
+
+        return self.parent.open(new, timeout=req.timeout)
+
+    http_error_301 = http_error_303 = http_error_307 = http_error_302
+
+    inf_msg = "The HTTP server returned a redirect error that would " \
+              "lead to an infinite loop.\n" \
+              "The last 30x error message was:\n"
+
+
+def _parse_proxy(proxy):
+    """Return (scheme, user, password, host/port) given a URL or an authority.
+
+    If a URL is supplied, it must have an authority (host:port) component.
+    According to RFC 3986, having an authority component means the URL must
+    have two slashes after the scheme:
+
+    >>> _parse_proxy('file:/ftp.example.com/')
+    Traceback (most recent call last):
+    ValueError: proxy URL with no authority: 'file:/ftp.example.com/'
+
+    The first three items of the returned tuple may be None.
+
+    Examples of authority parsing:
+
+    >>> _parse_proxy('proxy.example.com')
+    (None, None, None, 'proxy.example.com')
+    >>> _parse_proxy('proxy.example.com:3128')
+    (None, None, None, 'proxy.example.com:3128')
+
+    The authority component may optionally include userinfo (assumed to be
+    username:password):
+
+    >>> _parse_proxy('joe:password@proxy.example.com')
+    (None, 'joe', 'password', 'proxy.example.com')
+    >>> _parse_proxy('joe:password@proxy.example.com:3128')
+    (None, 'joe', 'password', 'proxy.example.com:3128')
+
+    Same examples, but with URLs instead:
+
+    >>> _parse_proxy('http://proxy.example.com/')
+    ('http', None, None, 'proxy.example.com')
+    >>> _parse_proxy('http://proxy.example.com:3128/')
+    ('http', None, None, 'proxy.example.com:3128')
+    >>> _parse_proxy('http://joe:password@proxy.example.com/')
+    ('http', 'joe', 'password', 'proxy.example.com')
+    >>> _parse_proxy('http://joe:password@proxy.example.com:3128')
+    ('http', 'joe', 'password', 'proxy.example.com:3128')
+
+    Everything after the authority is ignored:
+
+    >>> _parse_proxy('ftp://joe:password@proxy.example.com/rubbish:3128')
+    ('ftp', 'joe', 'password', 'proxy.example.com')
+
+    Test for no trailing '/' case:
+
+    >>> _parse_proxy('http://joe:password@proxy.example.com')
+    ('http', 'joe', 'password', 'proxy.example.com')
+
+    """
+    scheme, r_scheme = splittype(proxy)
+    if not r_scheme.startswith("/"):
+        # authority
+        scheme = None
+        authority = proxy
+    else:
+        # URL
+        if not r_scheme.startswith("//"):
+            raise ValueError("proxy URL with no authority: %r" % proxy)
+        # We have an authority, so for RFC 3986-compliant URLs (by ss 3.
+        # and 3.3.), path is empty or starts with '/'
+        end = r_scheme.find("/", 2)
+        if end == -1:
+            end = None
+        authority = r_scheme[2:end]
+    userinfo, hostport = splituser(authority)
+    if userinfo is not None:
+        user, password = splitpasswd(userinfo)
+    else:
+        user = password = None
+    return scheme, user, password, hostport
+
+class ProxyHandler(BaseHandler):
+    # Proxies must be in front
+    handler_order = 100
+
+    def __init__(self, proxies=None):
+        if proxies is None:
+            proxies = getproxies()
+        assert hasattr(proxies, 'keys'), "proxies must be a mapping"
+        self.proxies = proxies
+        for type, url in proxies.items():
+            setattr(self, '%s_open' % type,
+                    lambda r, proxy=url, type=type, meth=self.proxy_open:
+                        meth(r, proxy, type))
+
+    def proxy_open(self, req, proxy, type):
+        orig_type = req.type
+        proxy_type, user, password, hostport = _parse_proxy(proxy)
+        if proxy_type is None:
+            proxy_type = orig_type
+
+        if req.host and proxy_bypass(req.host):
+            return None
+
+        if user and password:
+            user_pass = '%s:%s' % (unquote(user),
+                                   unquote(password))
+            creds = base64.b64encode(user_pass.encode()).decode("ascii")
+            req.add_header('Proxy-authorization', 'Basic ' + creds)
+        hostport = unquote(hostport)
+        req.set_proxy(hostport, proxy_type)
+        if orig_type == proxy_type or orig_type == 'https':
+            # let other handlers take care of it
+            return None
+        else:
+            # need to start over, because the other handlers don't
+            # grok the proxy's URL type
+            # e.g. if we have a constructor arg proxies like so:
+            # {'http': 'ftp://proxy.example.com'}, we may end up turning
+            # a request for http://acme.example.com/a into one for
+            # ftp://proxy.example.com/a
+            return self.parent.open(req, timeout=req.timeout)
+
+class HTTPPasswordMgr(object):
+
+    def __init__(self):
+        self.passwd = {}
+
+    def add_password(self, realm, uri, user, passwd):
+        # uri could be a single URI or a sequence
+        if isinstance(uri, str):
+            uri = [uri]
+        if realm not in self.passwd:
+            self.passwd[realm] = {}
+        for default_port in True, False:
+            reduced_uri = tuple(
+                [self.reduce_uri(u, default_port) for u in uri])
+            self.passwd[realm][reduced_uri] = (user, passwd)
+
+    def find_user_password(self, realm, authuri):
+        domains = self.passwd.get(realm, {})
+        for default_port in True, False:
+            reduced_authuri = self.reduce_uri(authuri, default_port)
+            for uris, authinfo in domains.items():
+                for uri in uris:
+                    if self.is_suburi(uri, reduced_authuri):
+                        return authinfo
+        return None, None
+
+    def reduce_uri(self, uri, default_port=True):
+        """Accept authority or URI and extract only the authority and path."""
+        # note HTTP URLs do not have a userinfo component
+        parts = urlsplit(uri)
+        if parts[1]:
+            # URI
+            scheme = parts[0]
+            authority = parts[1]
+            path = parts[2] or '/'
+        else:
+            # host or host:port
+            scheme = None
+            authority = uri
+            path = '/'
+        host, port = splitport(authority)
+        if default_port and port is None and scheme is not None:
+            dport = {"http": 80,
+                     "https": 443,
+                     }.get(scheme)
+            if dport is not None:
+                authority = "%s:%d" % (host, dport)
+        return authority, path
+
+    def is_suburi(self, base, test):
+        """Check if test is below base in a URI tree
+
+        Both args must be URIs in reduced form.
+        """
+        if base == test:
+            return True
+        if base[0] != test[0]:
+            return False
+        common = posixpath.commonprefix((base[1], test[1]))
+        if len(common) == len(base[1]):
+            return True
+        return False
+
+
+class HTTPPasswordMgrWithDefaultRealm(HTTPPasswordMgr):
+
+    def find_user_password(self, realm, authuri):
+        user, password = HTTPPasswordMgr.find_user_password(self, realm,
+                                                            authuri)
+        if user is not None:
+            return user, password
+        return HTTPPasswordMgr.find_user_password(self, None, authuri)
+
+
+class AbstractBasicAuthHandler(object):
+
+    # XXX this allows for multiple auth-schemes, but will stupidly pick
+    # the last one with a realm specified.
+
+    # allow for double- and single-quoted realm values
+    # (single quotes are a violation of the RFC, but appear in the wild)
+    rx = re.compile('(?:.*,)*[ \t]*([^ \t]+)[ \t]+'
+                    'realm=(["\']?)([^"\']*)\\2', re.I)
+
+    # XXX could pre-emptively send auth info already accepted (RFC 2617,
+    # end of section 2, and section 1.2 immediately after "credentials"
+    # production).
+
+    def __init__(self, password_mgr=None):
+        if password_mgr is None:
+            password_mgr = HTTPPasswordMgr()
+        self.passwd = password_mgr
+        self.add_password = self.passwd.add_password
+        self.retried = 0
+
+    def reset_retry_count(self):
+        self.retried = 0
+
+    def http_error_auth_reqed(self, authreq, host, req, headers):
+        # host may be an authority (without userinfo) or a URL with an
+        # authority
+        # XXX could be multiple headers
+        authreq = headers.get(authreq, None)
+
+        if self.retried > 5:
+            # retry sending the username:password 5 times before failing.
+            raise HTTPError(req.get_full_url(), 401, "basic auth failed",
+                    headers, None)
+        else:
+            self.retried += 1
+
+        if authreq:
+            scheme = authreq.split()[0]
+            if scheme.lower() != 'basic':
+                raise ValueError("AbstractBasicAuthHandler does not"
+                                 " support the following scheme: '%s'" %
+                                 scheme)
+            else:
+                mo = AbstractBasicAuthHandler.rx.search(authreq)
+                if mo:
+                    scheme, quote, realm = mo.groups()
+                    if quote not in ['"',"'"]:
+                        warnings.warn("Basic Auth Realm was unquoted",
+                                      UserWarning, 2)
+                    if scheme.lower() == 'basic':
+                        response = self.retry_http_basic_auth(host, req, realm)
+                        if response and response.code != 401:
+                            self.retried = 0
+                        return response
+
+    def retry_http_basic_auth(self, host, req, realm):
+        user, pw = self.passwd.find_user_password(realm, host)
+        if pw is not None:
+            raw = "%s:%s" % (user, pw)
+            auth = "Basic " + base64.b64encode(raw.encode()).decode("ascii")
+            if req.headers.get(self.auth_header, None) == auth:
+                return None
+            req.add_unredirected_header(self.auth_header, auth)
+            return self.parent.open(req, timeout=req.timeout)
+        else:
+            return None
+
+
+class HTTPBasicAuthHandler(AbstractBasicAuthHandler, BaseHandler):
+
+    auth_header = 'Authorization'
+
+    def http_error_401(self, req, fp, code, msg, headers):
+        url = req.full_url
+        response = self.http_error_auth_reqed('www-authenticate',
+                                          url, req, headers)
+        self.reset_retry_count()
+        return response
+
+
+class ProxyBasicAuthHandler(AbstractBasicAuthHandler, BaseHandler):
+
+    auth_header = 'Proxy-authorization'
+
+    def http_error_407(self, req, fp, code, msg, headers):
+        # http_error_auth_reqed requires that there is no userinfo component in
+        # authority.  Assume there isn't one, since urllib.request does not (and
+        # should not, RFC 3986 s. 3.2.1) support requests for URLs containing
+        # userinfo.
+        authority = req.host
+        response = self.http_error_auth_reqed('proxy-authenticate',
+                                          authority, req, headers)
+        self.reset_retry_count()
+        return response
+
+
+# Return n random bytes.
+_randombytes = os.urandom
+
+
+class AbstractDigestAuthHandler(object):
+    # Digest authentication is specified in RFC 2617.
+
+    # XXX The client does not inspect the Authentication-Info header
+    # in a successful response.
+
+    # XXX It should be possible to test this implementation against
+    # a mock server that just generates a static set of challenges.
+
+    # XXX qop="auth-int" supports is shaky
+
+    def __init__(self, passwd=None):
+        if passwd is None:
+            passwd = HTTPPasswordMgr()
+        self.passwd = passwd
+        self.add_password = self.passwd.add_password
+        self.retried = 0
+        self.nonce_count = 0
+        self.last_nonce = None
+
+    def reset_retry_count(self):
+        self.retried = 0
+
+    def http_error_auth_reqed(self, auth_header, host, req, headers):
+        authreq = headers.get(auth_header, None)
+        if self.retried > 5:
+            # Don't fail endlessly - if we failed once, we'll probably
+            # fail a second time. Hm. Unless the Password Manager is
+            # prompting for the information. Crap. This isn't great
+            # but it's better than the current 'repeat until recursion
+            # depth exceeded' approach <wink>
+            raise HTTPError(req.full_url, 401, "digest auth failed",
+                            headers, None)
+        else:
+            self.retried += 1
+        if authreq:
+            scheme = authreq.split()[0]
+            if scheme.lower() == 'digest':
+                return self.retry_http_digest_auth(req, authreq)
+            elif scheme.lower() != 'basic':
+                raise ValueError("AbstractDigestAuthHandler does not support"
+                                 " the following scheme: '%s'" % scheme)
+
+    def retry_http_digest_auth(self, req, auth):
+        token, challenge = auth.split(' ', 1)
+        chal = parse_keqv_list(filter(None, parse_http_list(challenge)))
+        auth = self.get_authorization(req, chal)
+        if auth:
+            auth_val = 'Digest %s' % auth
+            if req.headers.get(self.auth_header, None) == auth_val:
+                return None
+            req.add_unredirected_header(self.auth_header, auth_val)
+            resp = self.parent.open(req, timeout=req.timeout)
+            return resp
+
+    def get_cnonce(self, nonce):
+        # The cnonce-value is an opaque
+        # quoted string value provided by the client and used by both client
+        # and server to avoid chosen plaintext attacks, to provide mutual
+        # authentication, and to provide some message integrity protection.
+        # This isn't a fabulous effort, but it's probably Good Enough.
+        s = "%s:%s:%s:" % (self.nonce_count, nonce, time.ctime())
+        b = s.encode("ascii") + _randombytes(8)
+        dig = hashlib.sha1(b).hexdigest()
+        return dig[:16]
+
+    def get_authorization(self, req, chal):
+        try:
+            realm = chal['realm']
+            nonce = chal['nonce']
+            qop = chal.get('qop')
+            algorithm = chal.get('algorithm', 'MD5')
+            # mod_digest doesn't send an opaque, even though it isn't
+            # supposed to be optional
+            opaque = chal.get('opaque', None)
+        except KeyError:
+            return None
+
+        H, KD = self.get_algorithm_impls(algorithm)
+        if H is None:
+            return None
+
+        user, pw = self.passwd.find_user_password(realm, req.full_url)
+        if user is None:
+            return None
+
+        # XXX not implemented yet
+        if req.data is not None:
+            entdig = self.get_entity_digest(req.data, chal)
+        else:
+            entdig = None
+
+        A1 = "%s:%s:%s" % (user, realm, pw)
+        A2 = "%s:%s" % (req.get_method(),
+                        # XXX selector: what about proxies and full urls
+                        req.selector)
+        if qop == 'auth':
+            if nonce == self.last_nonce:
+                self.nonce_count += 1
+            else:
+                self.nonce_count = 1
+                self.last_nonce = nonce
+            ncvalue = '%08x' % self.nonce_count
+            cnonce = self.get_cnonce(nonce)
+            noncebit = "%s:%s:%s:%s:%s" % (nonce, ncvalue, cnonce, qop, H(A2))
+            respdig = KD(H(A1), noncebit)
+        elif qop is None:
+            respdig = KD(H(A1), "%s:%s" % (nonce, H(A2)))
+        else:
+            # XXX handle auth-int.
+            raise URLError("qop '%s' is not supported." % qop)
+
+        # XXX should the partial digests be encoded too?
+
+        base = 'username="%s", realm="%s", nonce="%s", uri="%s", ' \
+               'response="%s"' % (user, realm, nonce, req.selector,
+                                  respdig)
+        if opaque:
+            base += ', opaque="%s"' % opaque
+        if entdig:
+            base += ', digest="%s"' % entdig
+        base += ', algorithm="%s"' % algorithm
+        if qop:
+            base += ', qop=auth, nc=%s, cnonce="%s"' % (ncvalue, cnonce)
+        return base
+
+    def get_algorithm_impls(self, algorithm):
+        # lambdas assume digest modules are imported at the top level
+        if algorithm == 'MD5':
+            H = lambda x: hashlib.md5(x.encode("ascii")).hexdigest()
+        elif algorithm == 'SHA':
+            H = lambda x: hashlib.sha1(x.encode("ascii")).hexdigest()
+        # XXX MD5-sess
+        KD = lambda s, d: H("%s:%s" % (s, d))
+        return H, KD
+
+    def get_entity_digest(self, data, chal):
+        # XXX not implemented yet
+        return None
+
+
+class HTTPDigestAuthHandler(BaseHandler, AbstractDigestAuthHandler):
+    """An authentication protocol defined by RFC 2069
+
+    Digest authentication improves on basic authentication because it
+    does not transmit passwords in the clear.
+    """
+
+    auth_header = 'Authorization'
+    handler_order = 490  # before Basic auth
+
+    def http_error_401(self, req, fp, code, msg, headers):
+        host = urlparse(req.full_url)[1]
+        retry = self.http_error_auth_reqed('www-authenticate',
+                                           host, req, headers)
+        self.reset_retry_count()
+        return retry
+
+
+class ProxyDigestAuthHandler(BaseHandler, AbstractDigestAuthHandler):
+
+    auth_header = 'Proxy-Authorization'
+    handler_order = 490  # before Basic auth
+
+    def http_error_407(self, req, fp, code, msg, headers):
+        host = req.host
+        retry = self.http_error_auth_reqed('proxy-authenticate',
+                                           host, req, headers)
+        self.reset_retry_count()
+        return retry
+
+class AbstractHTTPHandler(BaseHandler):
+
+    def __init__(self, debuglevel=0):
+        self._debuglevel = debuglevel
+
+    def set_http_debuglevel(self, level):
+        self._debuglevel = level
+
+    def do_request_(self, request):
+        host = request.host
+        if not host:
+            raise URLError('no host given')
+
+        if request.data is not None:  # POST
+            data = request.data
+            if isinstance(data, str):
+                msg = "POST data should be bytes or an iterable of bytes. " \
+                      "It cannot be of type str."
+                raise TypeError(msg)
+            if not request.has_header('Content-type'):
+                request.add_unredirected_header(
+                    'Content-type',
+                    'application/x-www-form-urlencoded')
+            if not request.has_header('Content-length'):
+                size = None
+                try:
+                    ### For Python-Future:
+                    if PY2 and isinstance(data, array.array):
+                        # memoryviews of arrays aren't supported
+                        # in Py2.7. (e.g. memoryview(array.array('I',
+                        # [1, 2, 3, 4])) raises a TypeError.)
+                        # So we calculate the size manually instead:
+                        size = len(data) * data.itemsize
+                    ###
+                    else:
+                        mv = memoryview(data)
+                        size = len(mv) * mv.itemsize
+                except TypeError:
+                    if isinstance(data, collections.Iterable):
+                        raise ValueError("Content-Length should be specified "
+                                "for iterable data of type %r %r" % (type(data),
+                                data))
+                else:
+                    request.add_unredirected_header(
+                            'Content-length', '%d' % size)
+
+        sel_host = host
+        if request.has_proxy():
+            scheme, sel = splittype(request.selector)
+            sel_host, sel_path = splithost(sel)
+        if not request.has_header('Host'):
+            request.add_unredirected_header('Host', sel_host)
+        for name, value in self.parent.addheaders:
+            name = name.capitalize()
+            if not request.has_header(name):
+                request.add_unredirected_header(name, value)
+
+        return request
+
+    def do_open(self, http_class, req, **http_conn_args):
+        """Return an HTTPResponse object for the request, using http_class.
+
+        http_class must implement the HTTPConnection API from http.client.
+        """
+        host = req.host
+        if not host:
+            raise URLError('no host given')
+
+        # will parse host:port
+        h = http_class(host, timeout=req.timeout, **http_conn_args)
+
+        headers = dict(req.unredirected_hdrs)
+        headers.update(dict((k, v) for k, v in req.headers.items()
+                            if k not in headers))
+
+        # TODO(jhylton): Should this be redesigned to handle
+        # persistent connections?
+
+        # We want to make an HTTP/1.1 request, but the addinfourl
+        # class isn't prepared to deal with a persistent connection.
+        # It will try to read all remaining data from the socket,
+        # which will block while the server waits for the next request.
+        # So make sure the connection gets closed after the (only)
+        # request.
+        headers["Connection"] = "close"
+        headers = dict((name.title(), val) for name, val in headers.items())
+
+        if req._tunnel_host:
+            tunnel_headers = {}
+            proxy_auth_hdr = "Proxy-Authorization"
+            if proxy_auth_hdr in headers:
+                tunnel_headers[proxy_auth_hdr] = headers[proxy_auth_hdr]
+                # Proxy-Authorization should not be sent to origin
+                # server.
+                del headers[proxy_auth_hdr]
+            h.set_tunnel(req._tunnel_host, headers=tunnel_headers)
+
+        try:
+            h.request(req.get_method(), req.selector, req.data, headers)
+        except socket.error as err: # timeout error
+            h.close()
+            raise URLError(err)
+        else:
+            r = h.getresponse()
+            # If the server does not send us a 'Connection: close' header,
+            # HTTPConnection assumes the socket should be left open. Manually
+            # mark the socket to be closed when this response object goes away.
+            if h.sock:
+                h.sock.close()
+                h.sock = None
+
+
+        r.url = req.get_full_url()
+        # This line replaces the .msg attribute of the HTTPResponse
+        # with .headers, because urllib clients expect the response to
+        # have the reason in .msg.  It would be good to mark this
+        # attribute is deprecated and get then to use info() or
+        # .headers.
+        r.msg = r.reason
+        return r
+
+
+class HTTPHandler(AbstractHTTPHandler):
+
+    def http_open(self, req):
+        return self.do_open(http_client.HTTPConnection, req)
+
+    http_request = AbstractHTTPHandler.do_request_
+
+if hasattr(http_client, 'HTTPSConnection'):
+
+    class HTTPSHandler(AbstractHTTPHandler):
+
+        def __init__(self, debuglevel=0, context=None, check_hostname=None):
+            AbstractHTTPHandler.__init__(self, debuglevel)
+            self._context = context
+            self._check_hostname = check_hostname
+
+        def https_open(self, req):
+            return self.do_open(http_client.HTTPSConnection, req,
+                context=self._context, check_hostname=self._check_hostname)
+
+        https_request = AbstractHTTPHandler.do_request_
+
+    __all__.append('HTTPSHandler')
+
+class HTTPCookieProcessor(BaseHandler):
+    def __init__(self, cookiejar=None):
+        import future.backports.http.cookiejar as http_cookiejar
+        if cookiejar is None:
+            cookiejar = http_cookiejar.CookieJar()
+        self.cookiejar = cookiejar
+
+    def http_request(self, request):
+        self.cookiejar.add_cookie_header(request)
+        return request
+
+    def http_response(self, request, response):
+        self.cookiejar.extract_cookies(response, request)
+        return response
+
+    https_request = http_request
+    https_response = http_response
+
+class UnknownHandler(BaseHandler):
+    def unknown_open(self, req):
+        type = req.type
+        raise URLError('unknown url type: %s' % type)
+
+def parse_keqv_list(l):
+    """Parse list of key=value strings where keys are not duplicated."""
+    parsed = {}
+    for elt in l:
+        k, v = elt.split('=', 1)
+        if v[0] == '"' and v[-1] == '"':
+            v = v[1:-1]
+        parsed[k] = v
+    return parsed
+
+def parse_http_list(s):
+    """Parse lists as described by RFC 2068 Section 2.
+
+    In particular, parse comma-separated lists where the elements of
+    the list may include quoted-strings.  A quoted-string could
+    contain a comma.  A non-quoted string could have quotes in the
+    middle.  Neither commas nor quotes count if they are escaped.
+    Only double-quotes count, not single-quotes.
+    """
+    res = []
+    part = ''
+
+    escape = quote = False
+    for cur in s:
+        if escape:
+            part += cur
+            escape = False
+            continue
+        if quote:
+            if cur == '\\':
+                escape = True
+                continue
+            elif cur == '"':
+                quote = False
+            part += cur
+            continue
+
+        if cur == ',':
+            res.append(part)
+            part = ''
+            continue
+
+        if cur == '"':
+            quote = True
+
+        part += cur
+
+    # append last part
+    if part:
+        res.append(part)
+
+    return [part.strip() for part in res]
+
+class FileHandler(BaseHandler):
+    # Use local file or FTP depending on form of URL
+    def file_open(self, req):
+        url = req.selector
+        if url[:2] == '//' and url[2:3] != '/' and (req.host and
+                req.host != 'localhost'):
+            if not req.host is self.get_names():
+                raise URLError("file:// scheme is supported only on localhost")
+        else:
+            return self.open_local_file(req)
+
+    # names for the localhost
+    names = None
+    def get_names(self):
+        if FileHandler.names is None:
+            try:
+                FileHandler.names = tuple(
+                    socket.gethostbyname_ex('localhost')[2] +
+                    socket.gethostbyname_ex(socket.gethostname())[2])
+            except socket.gaierror:
+                FileHandler.names = (socket.gethostbyname('localhost'),)
+        return FileHandler.names
+
+    # not entirely sure what the rules are here
+    def open_local_file(self, req):
+        import future.backports.email.utils as email_utils
+        import mimetypes
+        host = req.host
+        filename = req.selector
+        localfile = url2pathname(filename)
+        try:
+            stats = os.stat(localfile)
+            size = stats.st_size
+            modified = email_utils.formatdate(stats.st_mtime, usegmt=True)
+            mtype = mimetypes.guess_type(filename)[0]
+            headers = email.message_from_string(
+                'Content-type: %s\nContent-length: %d\nLast-modified: %s\n' %
+                (mtype or 'text/plain', size, modified))
+            if host:
+                host, port = splitport(host)
+            if not host or \
+                (not port and _safe_gethostbyname(host) in self.get_names()):
+                if host:
+                    origurl = 'file://' + host + filename
+                else:
+                    origurl = 'file://' + filename
+                return addinfourl(open(localfile, 'rb'), headers, origurl)
+        except OSError as exp:
+            # users shouldn't expect OSErrors coming from urlopen()
+            raise URLError(exp)
+        raise URLError('file not on local host')
+
+def _safe_gethostbyname(host):
+    try:
+        return socket.gethostbyname(host)
+    except socket.gaierror:
+        return None
+
+class FTPHandler(BaseHandler):
+    def ftp_open(self, req):
+        import ftplib
+        import mimetypes
+        host = req.host
+        if not host:
+            raise URLError('ftp error: no host given')
+        host, port = splitport(host)
+        if port is None:
+            port = ftplib.FTP_PORT
+        else:
+            port = int(port)
+
+        # username/password handling
+        user, host = splituser(host)
+        if user:
+            user, passwd = splitpasswd(user)
+        else:
+            passwd = None
+        host = unquote(host)
+        user = user or ''
+        passwd = passwd or ''
+
+        try:
+            host = socket.gethostbyname(host)
+        except socket.error as msg:
+            raise URLError(msg)
+        path, attrs = splitattr(req.selector)
+        dirs = path.split('/')
+        dirs = list(map(unquote, dirs))
+        dirs, file = dirs[:-1], dirs[-1]
+        if dirs and not dirs[0]:
+            dirs = dirs[1:]
+        try:
+            fw = self.connect_ftp(user, passwd, host, port, dirs, req.timeout)
+            type = file and 'I' or 'D'
+            for attr in attrs:
+                attr, value = splitvalue(attr)
+                if attr.lower() == 'type' and \
+                   value in ('a', 'A', 'i', 'I', 'd', 'D'):
+                    type = value.upper()
+            fp, retrlen = fw.retrfile(file, type)
+            headers = ""
+            mtype = mimetypes.guess_type(req.full_url)[0]
+            if mtype:
+                headers += "Content-type: %s\n" % mtype
+            if retrlen is not None and retrlen >= 0:
+                headers += "Content-length: %d\n" % retrlen
+            headers = email.message_from_string(headers)
+            return addinfourl(fp, headers, req.full_url)
+        except ftplib.all_errors as exp:
+            exc = URLError('ftp error: %r' % exp)
+            raise_with_traceback(exc)
+
+    def connect_ftp(self, user, passwd, host, port, dirs, timeout):
+        return ftpwrapper(user, passwd, host, port, dirs, timeout,
+                          persistent=False)
+
+class CacheFTPHandler(FTPHandler):
+    # XXX would be nice to have pluggable cache strategies
+    # XXX this stuff is definitely not thread safe
+    def __init__(self):
+        self.cache = {}
+        self.timeout = {}
+        self.soonest = 0
+        self.delay = 60
+        self.max_conns = 16
+
+    def setTimeout(self, t):
+        self.delay = t
+
+    def setMaxConns(self, m):
+        self.max_conns = m
+
+    def connect_ftp(self, user, passwd, host, port, dirs, timeout):
+        key = user, host, port, '/'.join(dirs), timeout
+        if key in self.cache:
+            self.timeout[key] = time.time() + self.delay
+        else:
+            self.cache[key] = ftpwrapper(user, passwd, host, port,
+                                         dirs, timeout)
+            self.timeout[key] = time.time() + self.delay
+        self.check_cache()
+        return self.cache[key]
+
+    def check_cache(self):
+        # first check for old ones
+        t = time.time()
+        if self.soonest <= t:
+            for k, v in list(self.timeout.items()):
+                if v < t:
+                    self.cache[k].close()
+                    del self.cache[k]
+                    del self.timeout[k]
+        self.soonest = min(list(self.timeout.values()))
+
+        # then check the size
+        if len(self.cache) == self.max_conns:
+            for k, v in list(self.timeout.items()):
+                if v == self.soonest:
+                    del self.cache[k]
+                    del self.timeout[k]
+                    break
+            self.soonest = min(list(self.timeout.values()))
+
+    def clear_cache(self):
+        for conn in self.cache.values():
+            conn.close()
+        self.cache.clear()
+        self.timeout.clear()
+
+
+# Code move from the old urllib module
+
+MAXFTPCACHE = 10        # Trim the ftp cache beyond this size
+
+# Helper for non-unix systems
+if os.name == 'nt':
+    from nturl2path import url2pathname, pathname2url
+else:
+    def url2pathname(pathname):
+        """OS-specific conversion from a relative URL of the 'file' scheme
+        to a file system path; not recommended for general use."""
+        return unquote(pathname)
+
+    def pathname2url(pathname):
+        """OS-specific conversion from a file system path to a relative URL
+        of the 'file' scheme; not recommended for general use."""
+        return quote(pathname)
+
+# This really consists of two pieces:
+# (1) a class which handles opening of all sorts of URLs
+#     (plus assorted utilities etc.)
+# (2) a set of functions for parsing URLs
+# XXX Should these be separated out into different modules?
+
+
+ftpcache = {}
+class URLopener(object):
+    """Class to open URLs.
+    This is a class rather than just a subroutine because we may need
+    more than one set of global protocol-specific options.
+    Note -- this is a base class for those who don't want the
+    automatic handling of errors type 302 (relocated) and 401
+    (authorization needed)."""
+
+    __tempfiles = None
+
+    version = "Python-urllib/%s" % __version__
+
+    # Constructor
+    def __init__(self, proxies=None, **x509):
+        msg = "%(class)s style of invoking requests is deprecated. " \
+              "Use newer urlopen functions/methods" % {'class': self.__class__.__name__}
+        warnings.warn(msg, DeprecationWarning, stacklevel=3)
+        if proxies is None:
+            proxies = getproxies()
+        assert hasattr(proxies, 'keys'), "proxies must be a mapping"
+        self.proxies = proxies
+        self.key_file = x509.get('key_file')
+        self.cert_file = x509.get('cert_file')
+        self.addheaders = [('User-Agent', self.version)]
+        self.__tempfiles = []
+        self.__unlink = os.unlink # See cleanup()
+        self.tempcache = None
+        # Undocumented feature: if you assign {} to tempcache,
+        # it is used to cache files retrieved with
+        # self.retrieve().  This is not enabled by default
+        # since it does not work for changing documents (and I
+        # haven't got the logic to check expiration headers
+        # yet).
+        self.ftpcache = ftpcache
+        # Undocumented feature: you can use a different
+        # ftp cache by assigning to the .ftpcache member;
+        # in case you want logically independent URL openers
+        # XXX This is not threadsafe.  Bah.
+
+    def __del__(self):
+        self.close()
+
+    def close(self):
+        self.cleanup()
+
+    def cleanup(self):
+        # This code sometimes runs when the rest of this module
+        # has already been deleted, so it can't use any globals
+        # or import anything.
+        if self.__tempfiles:
+            for file in self.__tempfiles:
+                try:
+                    self.__unlink(file)
+                except OSError:
+                    pass
+            del self.__tempfiles[:]
+        if self.tempcache:
+            self.tempcache.clear()
+
+    def addheader(self, *args):
+        """Add a header to be used by the HTTP interface only
+        e.g. u.addheader('Accept', 'sound/basic')"""
+        self.addheaders.append(args)
+
+    # External interface
+    def open(self, fullurl, data=None):
+        """Use URLopener().open(file) instead of open(file, 'r')."""
+        fullurl = unwrap(to_bytes(fullurl))
+        fullurl = quote(fullurl, safe="%/:=&?~#+!$,;'@()*[]|")
+        if self.tempcache and fullurl in self.tempcache:
+            filename, headers = self.tempcache[fullurl]
+            fp = open(filename, 'rb')
+            return addinfourl(fp, headers, fullurl)
+        urltype, url = splittype(fullurl)
+        if not urltype:
+            urltype = 'file'
+        if urltype in self.proxies:
+            proxy = self.proxies[urltype]
+            urltype, proxyhost = splittype(proxy)
+            host, selector = splithost(proxyhost)
+            url = (host, fullurl) # Signal special case to open_*()
+        else:
+            proxy = None
+        name = 'open_' + urltype
+        self.type = urltype
+        name = name.replace('-', '_')
+        if not hasattr(self, name):
+            if proxy:
+                return self.open_unknown_proxy(proxy, fullurl, data)
+            else:
+                return self.open_unknown(fullurl, data)
+        try:
+            if data is None:
+                return getattr(self, name)(url)
+            else:
+                return getattr(self, name)(url, data)
+        except HTTPError:
+            raise
+        except socket.error as msg:
+            raise_with_traceback(IOError('socket error', msg))
+
+    def open_unknown(self, fullurl, data=None):
+        """Overridable interface to open unknown URL type."""
+        type, url = splittype(fullurl)
+        raise IOError('url error', 'unknown url type', type)
+
+    def open_unknown_proxy(self, proxy, fullurl, data=None):
+        """Overridable interface to open unknown URL type."""
+        type, url = splittype(fullurl)
+        raise IOError('url error', 'invalid proxy for %s' % type, proxy)
+
+    # External interface
+    def retrieve(self, url, filename=None, reporthook=None, data=None):
+        """retrieve(url) returns (filename, headers) for a local object
+        or (tempfilename, headers) for a remote object."""
+        url = unwrap(to_bytes(url))
+        if self.tempcache and url in self.tempcache:
+            return self.tempcache[url]
+        type, url1 = splittype(url)
+        if filename is None and (not type or type == 'file'):
+            try:
+                fp = self.open_local_file(url1)
+                hdrs = fp.info()
+                fp.close()
+                return url2pathname(splithost(url1)[1]), hdrs
+            except IOError as msg:
+                pass
+        fp = self.open(url, data)
+        try:
+            headers = fp.info()
+            if filename:
+                tfp = open(filename, 'wb')
+            else:
+                import tempfile
+                garbage, path = splittype(url)
+                garbage, path = splithost(path or "")
+                path, garbage = splitquery(path or "")
+                path, garbage = splitattr(path or "")
+                suffix = os.path.splitext(path)[1]
+                (fd, filename) = tempfile.mkstemp(suffix)
+                self.__tempfiles.append(filename)
+                tfp = os.fdopen(fd, 'wb')
+            try:
+                result = filename, headers
+                if self.tempcache is not None:
+                    self.tempcache[url] = result
+                bs = 1024*8
+                size = -1
+                read = 0
+                blocknum = 0
+                if "content-length" in headers:
+                    size = int(headers["Content-Length"])
+                if reporthook:
+                    reporthook(blocknum, bs, size)
+                while 1:
+                    block = fp.read(bs)
+                    if not block:
+                        break
+                    read += len(block)
+                    tfp.write(block)
+                    blocknum += 1
+                    if reporthook:
+                        reporthook(blocknum, bs, size)
+            finally:
+                tfp.close()
+        finally:
+            fp.close()
+
+        # raise exception if actual size does not match content-length header
+        if size >= 0 and read < size:
+            raise ContentTooShortError(
+                "retrieval incomplete: got only %i out of %i bytes"
+                % (read, size), result)
+
+        return result
+
+    # Each method named open_<type> knows how to open that type of URL
+
+    def _open_generic_http(self, connection_factory, url, data):
+        """Make an HTTP connection using connection_class.
+
+        This is an internal method that should be called from
+        open_http() or open_https().
+
+        Arguments:
+        - connection_factory should take a host name and return an
+          HTTPConnection instance.
+        - url is the url to retrieval or a host, relative-path pair.
+        - data is payload for a POST request or None.
+        """
+
+        user_passwd = None
+        proxy_passwd= None
+        if isinstance(url, str):
+            host, selector = splithost(url)
+            if host:
+                user_passwd, host = splituser(host)
+                host = unquote(host)
+            realhost = host
+        else:
+            host, selector = url
+            # check whether the proxy contains authorization information
+            proxy_passwd, host = splituser(host)
+            # now we proceed with the url we want to obtain
+            urltype, rest = splittype(selector)
+            url = rest
+            user_passwd = None
+            if urltype.lower() != 'http':
+                realhost = None
+            else:
+                realhost, rest = splithost(rest)
+                if realhost:
+                    user_passwd, realhost = splituser(realhost)
+                if user_passwd:
+                    selector = "%s://%s%s" % (urltype, realhost, rest)
+                if proxy_bypass(realhost):
+                    host = realhost
+
+        if not host: raise IOError('http error', 'no host given')
+
+        if proxy_passwd:
+            proxy_passwd = unquote(proxy_passwd)
+            proxy_auth = base64.b64encode(proxy_passwd.encode()).decode('ascii')
+        else:
+            proxy_auth = None
+
+        if user_passwd:
+            user_passwd = unquote(user_passwd)
+            auth = base64.b64encode(user_passwd.encode()).decode('ascii')
+        else:
+            auth = None
+        http_conn = connection_factory(host)
+        headers = {}
+        if proxy_auth:
+            headers["Proxy-Authorization"] = "Basic %s" % proxy_auth
+        if auth:
+            headers["Authorization"] =  "Basic %s" % auth
+        if realhost:
+            headers["Host"] = realhost
+
+        # Add Connection:close as we don't support persistent connections yet.
+        # This helps in closing the socket and avoiding ResourceWarning
+
+        headers["Connection"] = "close"
+
+        for header, value in self.addheaders:
+            headers[header] = value
+
+        if data is not None:
+            headers["Content-Type"] = "application/x-www-form-urlencoded"
+            http_conn.request("POST", selector, data, headers)
+        else:
+            http_conn.request("GET", selector, headers=headers)
+
+        try:
+            response = http_conn.getresponse()
+        except http_client.BadStatusLine:
+            # something went wrong with the HTTP status line
+            raise URLError("http protocol error: bad status line")
+
+        # According to RFC 2616, "2xx" code indicates that the client's
+        # request was successfully received, understood, and accepted.
+        if 200 <= response.status < 300:
+            return addinfourl(response, response.msg, "http:" + url,
+                              response.status)
+        else:
+            return self.http_error(
+                url, response.fp,
+                response.status, response.reason, response.msg, data)
+
+    def open_http(self, url, data=None):
+        """Use HTTP protocol."""
+        return self._open_generic_http(http_client.HTTPConnection, url, data)
+
+    def http_error(self, url, fp, errcode, errmsg, headers, data=None):
+        """Handle http errors.
+
+        Derived class can override this, or provide specific handlers
+        named http_error_DDD where DDD is the 3-digit error code."""
+        # First check if there's a specific handler for this error
+        name = 'http_error_%d' % errcode
+        if hasattr(self, name):
+            method = getattr(self, name)
+            if data is None:
+                result = method(url, fp, errcode, errmsg, headers)
+            else:
+                result = method(url, fp, errcode, errmsg, headers, data)
+            if result: return result
+        return self.http_error_default(url, fp, errcode, errmsg, headers)
+
+    def http_error_default(self, url, fp, errcode, errmsg, headers):
+        """Default error handler: close the connection and raise IOError."""
+        fp.close()
+        raise HTTPError(url, errcode, errmsg, headers, None)
+
+    if _have_ssl:
+        def _https_connection(self, host):
+            return http_client.HTTPSConnection(host,
+                                           key_file=self.key_file,
+                                           cert_file=self.cert_file)
+
+        def open_https(self, url, data=None):
+            """Use HTTPS protocol."""
+            return self._open_generic_http(self._https_connection, url, data)
+
+    def open_file(self, url):
+        """Use local file or FTP depending on form of URL."""
+        if not isinstance(url, str):
+            raise URLError('file error: proxy support for file protocol currently not implemented')
+        if url[:2] == '//' and url[2:3] != '/' and url[2:12].lower() != 'localhost/':
+            raise ValueError("file:// scheme is supported only on localhost")
+        else:
+            return self.open_local_file(url)
+
+    def open_local_file(self, url):
+        """Use local file."""
+        import future.backports.email.utils as email_utils
+        import mimetypes
+        host, file = splithost(url)
+        localname = url2pathname(file)
+        try:
+            stats = os.stat(localname)
+        except OSError as e:
+            raise URLError(e.strerror, e.filename)
+        size = stats.st_size
+        modified = email_utils.formatdate(stats.st_mtime, usegmt=True)
+        mtype = mimetypes.guess_type(url)[0]
+        headers = email.message_from_string(
+            'Content-Type: %s\nContent-Length: %d\nLast-modified: %s\n' %
+            (mtype or 'text/plain', size, modified))
+        if not host:
+            urlfile = file
+            if file[:1] == '/':
+                urlfile = 'file://' + file
+            return addinfourl(open(localname, 'rb'), headers, urlfile)
+        host, port = splitport(host)
+        if (not port
+           and socket.gethostbyname(host) in ((localhost(),) + thishost())):
+            urlfile = file
+            if file[:1] == '/':
+                urlfile = 'file://' + file
+            elif file[:2] == './':
+                raise ValueError("local file url may start with / or file:. Unknown url of type: %s" % url)
+            return addinfourl(open(localname, 'rb'), headers, urlfile)
+        raise URLError('local file error: not on local host')
+
+    def open_ftp(self, url):
+        """Use FTP protocol."""
+        if not isinstance(url, str):
+            raise URLError('ftp error: proxy support for ftp protocol currently not implemented')
+        import mimetypes
+        host, path = splithost(url)
+        if not host: raise URLError('ftp error: no host given')
+        host, port = splitport(host)
+        user, host = splituser(host)
+        if user: user, passwd = splitpasswd(user)
+        else: passwd = None
+        host = unquote(host)
+        user = unquote(user or '')
+        passwd = unquote(passwd or '')
+        host = socket.gethostbyname(host)
+        if not port:
+            import ftplib
+            port = ftplib.FTP_PORT
+        else:
+            port = int(port)
+        path, attrs = splitattr(path)
+        path = unquote(path)
+        dirs = path.split('/')
+        dirs, file = dirs[:-1], dirs[-1]
+        if dirs and not dirs[0]: dirs = dirs[1:]
+        if dirs and not dirs[0]: dirs[0] = '/'
+        key = user, host, port, '/'.join(dirs)
+        # XXX thread unsafe!
+        if len(self.ftpcache) > MAXFTPCACHE:
+            # Prune the cache, rather arbitrarily
+            for k in self.ftpcache.keys():
+                if k != key:
+                    v = self.ftpcache[k]
+                    del self.ftpcache[k]
+                    v.close()
+        try:
+            if key not in self.ftpcache:
+                self.ftpcache[key] = \
+                    ftpwrapper(user, passwd, host, port, dirs)
+            if not file: type = 'D'
+            else: type = 'I'
+            for attr in attrs:
+                attr, value = splitvalue(attr)
+                if attr.lower() == 'type' and \
+                   value in ('a', 'A', 'i', 'I', 'd', 'D'):
+                    type = value.upper()
+            (fp, retrlen) = self.ftpcache[key].retrfile(file, type)
+            mtype = mimetypes.guess_type("ftp:" + url)[0]
+            headers = ""
+            if mtype:
+                headers += "Content-Type: %s\n" % mtype
+            if retrlen is not None and retrlen >= 0:
+                headers += "Content-Length: %d\n" % retrlen
+            headers = email.message_from_string(headers)
+            return addinfourl(fp, headers, "ftp:" + url)
+        except ftperrors() as exp:
+            raise_with_traceback(URLError('ftp error %r' % exp))
+
+    def open_data(self, url, data=None):
+        """Use "data" URL."""
+        if not isinstance(url, str):
+            raise URLError('data error: proxy support for data protocol currently not implemented')
+        # ignore POSTed data
+        #
+        # syntax of data URLs:
+        # dataurl   := "data:" [ mediatype ] [ ";base64" ] "," data
+        # mediatype := [ type "/" subtype ] *( ";" parameter )
+        # data      := *urlchar
+        # parameter := attribute "=" value
+        try:
+            [type, data] = url.split(',', 1)
+        except ValueError:
+            raise IOError('data error', 'bad data URL')
+        if not type:
+            type = 'text/plain;charset=US-ASCII'
+        semi = type.rfind(';')
+        if semi >= 0 and '=' not in type[semi:]:
+            encoding = type[semi+1:]
+            type = type[:semi]
+        else:
+            encoding = ''
+        msg = []
+        msg.append('Date: %s'%time.strftime('%a, %d %b %Y %H:%M:%S GMT',
+                                            time.gmtime(time.time())))
+        msg.append('Content-type: %s' % type)
+        if encoding == 'base64':
+            # XXX is this encoding/decoding ok?
+            data = base64.decodebytes(data.encode('ascii')).decode('latin-1')
+        else:
+            data = unquote(data)
+        msg.append('Content-Length: %d' % len(data))
+        msg.append('')
+        msg.append(data)
+        msg = '\n'.join(msg)
+        headers = email.message_from_string(msg)
+        f = io.StringIO(msg)
+        #f.fileno = None     # needed for addinfourl
+        return addinfourl(f, headers, url)
+
+
+class FancyURLopener(URLopener):
+    """Derived class with handlers for errors we can handle (perhaps)."""
+
+    def __init__(self, *args, **kwargs):
+        URLopener.__init__(self, *args, **kwargs)
+        self.auth_cache = {}
+        self.tries = 0
+        self.maxtries = 10
+
+    def http_error_default(self, url, fp, errcode, errmsg, headers):
+        """Default error handling -- don't raise an exception."""
+        return addinfourl(fp, headers, "http:" + url, errcode)
+
+    def http_error_302(self, url, fp, errcode, errmsg, headers, data=None):
+        """Error 302 -- relocated (temporarily)."""
+        self.tries += 1
+        if self.maxtries and self.tries >= self.maxtries:
+            if hasattr(self, "http_error_500"):
+                meth = self.http_error_500
+            else:
+                meth = self.http_error_default
+            self.tries = 0
+            return meth(url, fp, 500,
+                        "Internal Server Error: Redirect Recursion", headers)
+        result = self.redirect_internal(url, fp, errcode, errmsg, headers,
+                                        data)
+        self.tries = 0
+        return result
+
+    def redirect_internal(self, url, fp, errcode, errmsg, headers, data):
+        if 'location' in headers:
+            newurl = headers['location']
+        elif 'uri' in headers:
+            newurl = headers['uri']
+        else:
+            return
+        fp.close()
+
+        # In case the server sent a relative URL, join with original:
+        newurl = urljoin(self.type + ":" + url, newurl)
+
+        urlparts = urlparse(newurl)
+
+        # For security reasons, we don't allow redirection to anything other
+        # than http, https and ftp.
+
+        # We are using newer HTTPError with older redirect_internal method
+        # This older method will get deprecated in 3.3
+
+        if urlparts.scheme not in ('http', 'https', 'ftp', ''):
+            raise HTTPError(newurl, errcode,
+                            errmsg +
+                            " Redirection to url '%s' is not allowed." % newurl,
+                            headers, fp)
+
+        return self.open(newurl)
+
+    def http_error_301(self, url, fp, errcode, errmsg, headers, data=None):
+        """Error 301 -- also relocated (permanently)."""
+        return self.http_error_302(url, fp, errcode, errmsg, headers, data)
+
+    def http_error_303(self, url, fp, errcode, errmsg, headers, data=None):
+        """Error 303 -- also relocated (essentially identical to 302)."""
+        return self.http_error_302(url, fp, errcode, errmsg, headers, data)
+
+    def http_error_307(self, url, fp, errcode, errmsg, headers, data=None):
+        """Error 307 -- relocated, but turn POST into error."""
+        if data is None:
+            return self.http_error_302(url, fp, errcode, errmsg, headers, data)
+        else:
+            return self.http_error_default(url, fp, errcode, errmsg, headers)
+
+    def http_error_401(self, url, fp, errcode, errmsg, headers, data=None,
+            retry=False):
+        """Error 401 -- authentication required.
+        This function supports Basic authentication only."""
+        if 'www-authenticate' not in headers:
+            URLopener.http_error_default(self, url, fp,
+                                         errcode, errmsg, headers)
+        stuff = headers['www-authenticate']
+        match = re.match('[ \t]*([^ \t]+)[ \t]+realm="([^"]*)"', stuff)
+        if not match:
+            URLopener.http_error_default(self, url, fp,
+                                         errcode, errmsg, headers)
+        scheme, realm = match.groups()
+        if scheme.lower() != 'basic':
+            URLopener.http_error_default(self, url, fp,
+                                         errcode, errmsg, headers)
+        if not retry:
+            URLopener.http_error_default(self, url, fp, errcode, errmsg,
+                    headers)
+        name = 'retry_' + self.type + '_basic_auth'
+        if data is None:
+            return getattr(self,name)(url, realm)
+        else:
+            return getattr(self,name)(url, realm, data)
+
+    def http_error_407(self, url, fp, errcode, errmsg, headers, data=None,
+            retry=False):
+        """Error 407 -- proxy authentication required.
+        This function supports Basic authentication only."""
+        if 'proxy-authenticate' not in headers:
+            URLopener.http_error_default(self, url, fp,
+                                         errcode, errmsg, headers)
+        stuff = headers['proxy-authenticate']
+        match = re.match('[ \t]*([^ \t]+)[ \t]+realm="([^"]*)"', stuff)
+        if not match:
+            URLopener.http_error_default(self, url, fp,
+                                         errcode, errmsg, headers)
+        scheme, realm = match.groups()
+        if scheme.lower() != 'basic':
+            URLopener.http_error_default(self, url, fp,
+                                         errcode, errmsg, headers)
+        if not retry:
+            URLopener.http_error_default(self, url, fp, errcode, errmsg,
+                    headers)
+        name = 'retry_proxy_' + self.type + '_basic_auth'
+        if data is None:
+            return getattr(self,name)(url, realm)
+        else:
+            return getattr(self,name)(url, realm, data)
+
+    def retry_proxy_http_basic_auth(self, url, realm, data=None):
+        host, selector = splithost(url)
+        newurl = 'http://' + host + selector
+        proxy = self.proxies['http']
+        urltype, proxyhost = splittype(proxy)
+        proxyhost, proxyselector = splithost(proxyhost)
+        i = proxyhost.find('@') + 1
+        proxyhost = proxyhost[i:]
+        user, passwd = self.get_user_passwd(proxyhost, realm, i)
+        if not (user or passwd): return None
+        proxyhost = "%s:%s@%s" % (quote(user, safe=''),
+                                  quote(passwd, safe=''), proxyhost)
+        self.proxies['http'] = 'http://' + proxyhost + proxyselector
+        if data is None:
+            return self.open(newurl)
+        else:
+            return self.open(newurl, data)
+
+    def retry_proxy_https_basic_auth(self, url, realm, data=None):
+        host, selector = splithost(url)
+        newurl = 'https://' + host + selector
+        proxy = self.proxies['https']
+        urltype, proxyhost = splittype(proxy)
+        proxyhost, proxyselector = splithost(proxyhost)
+        i = proxyhost.find('@') + 1
+        proxyhost = proxyhost[i:]
+        user, passwd = self.get_user_passwd(proxyhost, realm, i)
+        if not (user or passwd): return None
+        proxyhost = "%s:%s@%s" % (quote(user, safe=''),
+                                  quote(passwd, safe=''), proxyhost)
+        self.proxies['https'] = 'https://' + proxyhost + proxyselector
+        if data is None:
+            return self.open(newurl)
+        else:
+            return self.open(newurl, data)
+
+    def retry_http_basic_auth(self, url, realm, data=None):
+        host, selector = splithost(url)
+        i = host.find('@') + 1
+        host = host[i:]
+        user, passwd = self.get_user_passwd(host, realm, i)
+        if not (user or passwd): return None
+        host = "%s:%s@%s" % (quote(user, safe=''),
+                             quote(passwd, safe=''), host)
+        newurl = 'http://' + host + selector
+        if data is None:
+            return self.open(newurl)
+        else:
+            return self.open(newurl, data)
+
+    def retry_https_basic_auth(self, url, realm, data=None):
+        host, selector = splithost(url)
+        i = host.find('@') + 1
+        host = host[i:]
+        user, passwd = self.get_user_passwd(host, realm, i)
+        if not (user or passwd): return None
+        host = "%s:%s@%s" % (quote(user, safe=''),
+                             quote(passwd, safe=''), host)
+        newurl = 'https://' + host + selector
+        if data is None:
+            return self.open(newurl)
+        else:
+            return self.open(newurl, data)
+
+    def get_user_passwd(self, host, realm, clear_cache=0):
+        key = realm + '@' + host.lower()
+        if key in self.auth_cache:
+            if clear_cache:
+                del self.auth_cache[key]
+            else:
+                return self.auth_cache[key]
+        user, passwd = self.prompt_user_passwd(host, realm)
+        if user or passwd: self.auth_cache[key] = (user, passwd)
+        return user, passwd
+
+    def prompt_user_passwd(self, host, realm):
+        """Override this in a GUI environment!"""
+        import getpass
+        try:
+            user = input("Enter username for %s at %s: " % (realm, host))
+            passwd = getpass.getpass("Enter password for %s in %s at %s: " %
+                (user, realm, host))
+            return user, passwd
+        except KeyboardInterrupt:
+            print()
+            return None, None
+
+
+# Utility functions
+
+_localhost = None
+def localhost():
+    """Return the IP address of the magic hostname 'localhost'."""
+    global _localhost
+    if _localhost is None:
+        _localhost = socket.gethostbyname('localhost')
+    return _localhost
+
+_thishost = None
+def thishost():
+    """Return the IP addresses of the current host."""
+    global _thishost
+    if _thishost is None:
+        try:
+            _thishost = tuple(socket.gethostbyname_ex(socket.gethostname())[2])
+        except socket.gaierror:
+            _thishost = tuple(socket.gethostbyname_ex('localhost')[2])
+    return _thishost
+
+_ftperrors = None
+def ftperrors():
+    """Return the set of errors raised by the FTP class."""
+    global _ftperrors
+    if _ftperrors is None:
+        import ftplib
+        _ftperrors = ftplib.all_errors
+    return _ftperrors
+
+_noheaders = None
+def noheaders():
+    """Return an empty email Message object."""
+    global _noheaders
+    if _noheaders is None:
+        _noheaders = email.message_from_string("")
+    return _noheaders
+
+
+# Utility classes
+
+class ftpwrapper(object):
+    """Class used by open_ftp() for cache of open FTP connections."""
+
+    def __init__(self, user, passwd, host, port, dirs, timeout=None,
+                 persistent=True):
+        self.user = user
+        self.passwd = passwd
+        self.host = host
+        self.port = port
+        self.dirs = dirs
+        self.timeout = timeout
+        self.refcount = 0
+        self.keepalive = persistent
+        self.init()
+
+    def init(self):
+        import ftplib
+        self.busy = 0
+        self.ftp = ftplib.FTP()
+        self.ftp.connect(self.host, self.port, self.timeout)
+        self.ftp.login(self.user, self.passwd)
+        _target = '/'.join(self.dirs)
+        self.ftp.cwd(_target)
+
+    def retrfile(self, file, type):
+        import ftplib
+        self.endtransfer()
+        if type in ('d', 'D'): cmd = 'TYPE A'; isdir = 1
+        else: cmd = 'TYPE ' + type; isdir = 0
+        try:
+            self.ftp.voidcmd(cmd)
+        except ftplib.all_errors:
+            self.init()
+            self.ftp.voidcmd(cmd)
+        conn = None
+        if file and not isdir:
+            # Try to retrieve as a file
+            try:
+                cmd = 'RETR ' + file
+                conn, retrlen = self.ftp.ntransfercmd(cmd)
+            except ftplib.error_perm as reason:
+                if str(reason)[:3] != '550':
+                    raise_with_traceback(URLError('ftp error: %r' % reason))
+        if not conn:
+            # Set transfer mode to ASCII!
+            self.ftp.voidcmd('TYPE A')
+            # Try a directory listing. Verify that directory exists.
+            if file:
+                pwd = self.ftp.pwd()
+                try:
+                    try:
+                        self.ftp.cwd(file)
+                    except ftplib.error_perm as reason:
+                        ### Was:
+                        # raise URLError('ftp error: %r' % reason) from reason
+                        exc = URLError('ftp error: %r' % reason)
+                        exc.__cause__ = reason
+                        raise exc
+                finally:
+                    self.ftp.cwd(pwd)
+                cmd = 'LIST ' + file
+            else:
+                cmd = 'LIST'
+            conn, retrlen = self.ftp.ntransfercmd(cmd)
+        self.busy = 1
+
+        ftpobj = addclosehook(conn.makefile('rb'), self.file_close)
+        self.refcount += 1
+        conn.close()
+        # Pass back both a suitably decorated object and a retrieval length
+        return (ftpobj, retrlen)
+
+    def endtransfer(self):
+        self.busy = 0
+
+    def close(self):
+        self.keepalive = False
+        if self.refcount <= 0:
+            self.real_close()
+
+    def file_close(self):
+        self.endtransfer()
+        self.refcount -= 1
+        if self.refcount <= 0 and not self.keepalive:
+            self.real_close()
+
+    def real_close(self):
+        self.endtransfer()
+        try:
+            self.ftp.close()
+        except ftperrors():
+            pass
+
+# Proxy handling
+def getproxies_environment():
+    """Return a dictionary of scheme -> proxy server URL mappings.
+
+    Scan the environment for variables named <scheme>_proxy;
+    this seems to be the standard convention.  If you need a
+    different way, you can pass a proxies dictionary to the
+    [Fancy]URLopener constructor.
+
+    """
+    proxies = {}
+    for name, value in os.environ.items():
+        name = name.lower()
+        if value and name[-6:] == '_proxy':
+            proxies[name[:-6]] = value
+    return proxies
+
+def proxy_bypass_environment(host):
+    """Test if proxies should not be used for a particular host.
+
+    Checks the environment for a variable named no_proxy, which should
+    be a list of DNS suffixes separated by commas, or '*' for all hosts.
+    """
+    no_proxy = os.environ.get('no_proxy', '') or os.environ.get('NO_PROXY', '')
+    # '*' is special case for always bypass
+    if no_proxy == '*':
+        return 1
+    # strip port off host
+    hostonly, port = splitport(host)
+    # check if the host ends with any of the DNS suffixes
+    no_proxy_list = [proxy.strip() for proxy in no_proxy.split(',')]
+    for name in no_proxy_list:
+        if name and (hostonly.endswith(name) or host.endswith(name)):
+            return 1
+    # otherwise, don't bypass
+    return 0
+
+
+# This code tests an OSX specific data structure but is testable on all
+# platforms
+def _proxy_bypass_macosx_sysconf(host, proxy_settings):
+    """
+    Return True iff this host shouldn't be accessed using a proxy
+
+    This function uses the MacOSX framework SystemConfiguration
+    to fetch the proxy information.
+
+    proxy_settings come from _scproxy._get_proxy_settings or get mocked ie:
+    { 'exclude_simple': bool,
+      'exceptions': ['foo.bar', '*.bar.com', '127.0.0.1', '10.1', '10.0/16']
+    }
+    """
+    from fnmatch import fnmatch
+
+    hostonly, port = splitport(host)
+
+    def ip2num(ipAddr):
+        parts = ipAddr.split('.')
+        parts = list(map(int, parts))
+        if len(parts) != 4:
+            parts = (parts + [0, 0, 0, 0])[:4]
+        return (parts[0] << 24) | (parts[1] << 16) | (parts[2] << 8) | parts[3]
+
+    # Check for simple host names:
+    if '.' not in host:
+        if proxy_settings['exclude_simple']:
+            return True
+
+    hostIP = None
+
+    for value in proxy_settings.get('exceptions', ()):
+        # Items in the list are strings like these: *.local, 169.254/16
+        if not value: continue
+
+        m = re.match(r"(\d+(?:\.\d+)*)(/\d+)?", value)
+        if m is not None:
+            if hostIP is None:
+                try:
+                    hostIP = socket.gethostbyname(hostonly)
+                    hostIP = ip2num(hostIP)
+                except socket.error:
+                    continue
+
+            base = ip2num(m.group(1))
+            mask = m.group(2)
+            if mask is None:
+                mask = 8 * (m.group(1).count('.') + 1)
+            else:
+                mask = int(mask[1:])
+            mask = 32 - mask
+
+            if (hostIP >> mask) == (base >> mask):
+                return True
+
+        elif fnmatch(host, value):
+            return True
+
+    return False
+
+
+if sys.platform == 'darwin':
+    from _scproxy import _get_proxy_settings, _get_proxies
+
+    def proxy_bypass_macosx_sysconf(host):
+        proxy_settings = _get_proxy_settings()
+        return _proxy_bypass_macosx_sysconf(host, proxy_settings)
+
+    def getproxies_macosx_sysconf():
+        """Return a dictionary of scheme -> proxy server URL mappings.
+
+        This function uses the MacOSX framework SystemConfiguration
+        to fetch the proxy information.
+        """
+        return _get_proxies()
+
+
+
+    def proxy_bypass(host):
+        if getproxies_environment():
+            return proxy_bypass_environment(host)
+        else:
+            return proxy_bypass_macosx_sysconf(host)
+
+    def getproxies():
+        return getproxies_environment() or getproxies_macosx_sysconf()
+
+
+elif os.name == 'nt':
+    def getproxies_registry():
+        """Return a dictionary of scheme -> proxy server URL mappings.
+
+        Win32 uses the registry to store proxies.
+
+        """
+        proxies = {}
+        try:
+            import winreg
+        except ImportError:
+            # Std module, so should be around - but you never know!
+            return proxies
+        try:
+            internetSettings = winreg.OpenKey(winreg.HKEY_CURRENT_USER,
+                r'Software\Microsoft\Windows\CurrentVersion\Internet Settings')
+            proxyEnable = winreg.QueryValueEx(internetSettings,
+                                               'ProxyEnable')[0]
+            if proxyEnable:
+                # Returned as Unicode but problems if not converted to ASCII
+                proxyServer = str(winreg.QueryValueEx(internetSettings,
+                                                       'ProxyServer')[0])
+                if '=' in proxyServer:
+                    # Per-protocol settings
+                    for p in proxyServer.split(';'):
+                        protocol, address = p.split('=', 1)
+                        # See if address has a type:// prefix
+                        if not re.match('^([^/:]+)://', address):
+                            address = '%s://%s' % (protocol, address)
+                        proxies[protocol] = address
+                else:
+                    # Use one setting for all protocols
+                    if proxyServer[:5] == 'http:':
+                        proxies['http'] = proxyServer
+                    else:
+                        proxies['http'] = 'http://%s' % proxyServer
+                        proxies['https'] = 'https://%s' % proxyServer
+                        proxies['ftp'] = 'ftp://%s' % proxyServer
+            internetSettings.Close()
+        except (WindowsError, ValueError, TypeError):
+            # Either registry key not found etc, or the value in an
+            # unexpected format.
+            # proxies already set up to be empty so nothing to do
+            pass
+        return proxies
+
+    def getproxies():
+        """Return a dictionary of scheme -> proxy server URL mappings.
+
+        Returns settings gathered from the environment, if specified,
+        or the registry.
+
+        """
+        return getproxies_environment() or getproxies_registry()
+
+    def proxy_bypass_registry(host):
+        try:
+            import winreg
+        except ImportError:
+            # Std modules, so should be around - but you never know!
+            return 0
+        try:
+            internetSettings = winreg.OpenKey(winreg.HKEY_CURRENT_USER,
+                r'Software\Microsoft\Windows\CurrentVersion\Internet Settings')
+            proxyEnable = winreg.QueryValueEx(internetSettings,
+                                               'ProxyEnable')[0]
+            proxyOverride = str(winreg.QueryValueEx(internetSettings,
+                                                     'ProxyOverride')[0])
+            # ^^^^ Returned as Unicode but problems if not converted to ASCII
+        except WindowsError:
+            return 0
+        if not proxyEnable or not proxyOverride:
+            return 0
+        # try to make a host list from name and IP address.
+        rawHost, port = splitport(host)
+        host = [rawHost]
+        try:
+            addr = socket.gethostbyname(rawHost)
+            if addr != rawHost:
+                host.append(addr)
+        except socket.error:
+            pass
+        try:
+            fqdn = socket.getfqdn(rawHost)
+            if fqdn != rawHost:
+                host.append(fqdn)
+        except socket.error:
+            pass
+        # make a check value list from the registry entry: replace the
+        # '<local>' string by the localhost entry and the corresponding
+        # canonical entry.
+        proxyOverride = proxyOverride.split(';')
+        # now check if we match one of the registry values.
+        for test in proxyOverride:
+            if test == '<local>':
+                if '.' not in rawHost:
+                    return 1
+            test = test.replace(".", r"\.")     # mask dots
+            test = test.replace("*", r".*")     # change glob sequence
+            test = test.replace("?", r".")      # change glob char
+            for val in host:
+                if re.match(test, val, re.I):
+                    return 1
+        return 0
+
+    def proxy_bypass(host):
+        """Return a dictionary of scheme -> proxy server URL mappings.
+
+        Returns settings gathered from the environment, if specified,
+        or the registry.
+
+        """
+        if getproxies_environment():
+            return proxy_bypass_environment(host)
+        else:
+            return proxy_bypass_registry(host)
+
+else:
+    # By default use environment variables
+    getproxies = getproxies_environment
+    proxy_bypass = proxy_bypass_environment