Added OAuth2 authentication to apply_issue

third_party/httplib2/__init__.py

+from __future__ import generators
+"""
+httplib2
+
+A caching http interface that supports ETags and gzip
+to conserve bandwidth.
+
+Requires Python 2.3 or later
+
+Changelog:
+2007-08-18, Rick: Modified so it's able to use a socks proxy if needed.
+
+"""
+
+__author__ = "Joe Gregorio (joe@bitworking.org)"
+__copyright__ = "Copyright 2006, Joe Gregorio"
+__contributors__ = ["Thomas Broyer (t.broyer@ltgt.net)",
+                    "James Antill",
+                    "Xavier Verges Farrero",
+                    "Jonathan Feinberg",
+                    "Blair Zajac",
+                    "Sam Ruby",
+                    "Louis Nyffenegger"]
+__license__ = "MIT"
+__version__ = "0.8"
+
+import re
+import sys
+import email
+import email.Utils
+import email.Message
+import email.FeedParser
+import StringIO
+import gzip
+import zlib
+import httplib
+import urlparse
+import urllib
+import base64
+import os
+import copy
+import calendar
+import time
+import random
+import errno
+try:
+    from hashlib import sha1 as _sha, md5 as _md5
+except ImportError:
+    # prior to Python 2.5, these were separate modules
+    import sha
+    import md5
+    _sha = sha.new
+    _md5 = md5.new
+import hmac
+from gettext import gettext as _
+import socket
+
+try:
+    from httplib2 import socks
+except ImportError:
+    try:
+        import socks
+    except (ImportError, AttributeError):
+        socks = None
+
+# Build the appropriate socket wrapper for ssl
+try:
+    import ssl # python 2.6
+    ssl_SSLError = ssl.SSLError
+    def _ssl_wrap_socket(sock, key_file, cert_file,
+                         disable_validation, ca_certs):
+        if disable_validation:
+            cert_reqs = ssl.CERT_NONE
+        else:
+            cert_reqs = ssl.CERT_REQUIRED
+        # We should be specifying SSL version 3 or TLS v1, but the ssl module
+        # doesn't expose the necessary knobs. So we need to go with the default
+        # of SSLv23.
+        return ssl.wrap_socket(sock, keyfile=key_file, certfile=cert_file,
+                               cert_reqs=cert_reqs, ca_certs=ca_certs)
+except (AttributeError, ImportError):
+    ssl_SSLError = None
+    def _ssl_wrap_socket(sock, key_file, cert_file,
+                         disable_validation, ca_certs):
+        if not disable_validation:
+            raise CertificateValidationUnsupported(
+                    "SSL certificate validation is not supported without "
+                    "the ssl module installed. To avoid this error, install "
+                    "the ssl module, or explicity disable validation.")
+        ssl_sock = socket.ssl(sock, key_file, cert_file)
+        return httplib.FakeSocket(sock, ssl_sock)
+
+
+if sys.version_info >= (2,3):
+    from iri2uri import iri2uri
+else:
+    def iri2uri(uri):
+        return uri
+
+def has_timeout(timeout): # python 2.6
+    if hasattr(socket, '_GLOBAL_DEFAULT_TIMEOUT'):
+        return (timeout is not None and timeout is not socket._GLOBAL_DEFAULT_TIMEOUT)
+    return (timeout is not None)
+
+__all__ = [
+    'Http', 'Response', 'ProxyInfo', 'HttpLib2Error', 'RedirectMissingLocation',
+    'RedirectLimit', 'FailedToDecompressContent',
+    'UnimplementedDigestAuthOptionError',
+    'UnimplementedHmacDigestAuthOptionError',
+    'debuglevel', 'ProxiesUnavailableError']
+
+
+# The httplib debug level, set to a non-zero value to get debug output
+debuglevel = 0
+
+# A request will be tried 'RETRIES' times if it fails at the socket/connection level.
+RETRIES = 2
+
+# Python 2.3 support
+if sys.version_info < (2,4):
+    def sorted(seq):
+        seq.sort()
+        return seq
+
+# Python 2.3 support
+def HTTPResponse__getheaders(self):
+    """Return list of (header, value) tuples."""
+    if self.msg is None:
+        raise httplib.ResponseNotReady()
+    return self.msg.items()
+
+if not hasattr(httplib.HTTPResponse, 'getheaders'):
+    httplib.HTTPResponse.getheaders = HTTPResponse__getheaders
+
+# All exceptions raised here derive from HttpLib2Error
+class HttpLib2Error(Exception): pass
+
+# Some exceptions can be caught and optionally
+# be turned back into responses.
+class HttpLib2ErrorWithResponse(HttpLib2Error):
+    def __init__(self, desc, response, content):
+        self.response = response
+        self.content = content
+        HttpLib2Error.__init__(self, desc)
+
+class RedirectMissingLocation(HttpLib2ErrorWithResponse): pass
+class RedirectLimit(HttpLib2ErrorWithResponse): pass
+class FailedToDecompressContent(HttpLib2ErrorWithResponse): pass
+class UnimplementedDigestAuthOptionError(HttpLib2ErrorWithResponse): pass
+class UnimplementedHmacDigestAuthOptionError(HttpLib2ErrorWithResponse): pass
+
+class MalformedHeader(HttpLib2Error): pass
+class RelativeURIError(HttpLib2Error): pass
+class ServerNotFoundError(HttpLib2Error): pass
+class ProxiesUnavailableError(HttpLib2Error): pass
+class CertificateValidationUnsupported(HttpLib2Error): pass
+class SSLHandshakeError(HttpLib2Error): pass
+class NotSupportedOnThisPlatform(HttpLib2Error): pass
+class CertificateHostnameMismatch(SSLHandshakeError):
+    def __init__(self, desc, host, cert):
+        HttpLib2Error.__init__(self, desc)
+        self.host = host
+        self.cert = cert
+
+# Open Items:
+# -----------
+# Proxy support
+
+# Are we removing the cached content too soon on PUT (only delete on 200 Maybe?)
+
+# Pluggable cache storage (supports storing the cache in
+#   flat files by default. We need a plug-in architecture
+#   that can support Berkeley DB and Squid)
+
+# == Known Issues ==
+# Does not handle a resource that uses conneg and Last-Modified but no ETag as a cache validator.
+# Does not handle Cache-Control: max-stale
+# Does not use Age: headers when calculating cache freshness.
+
+
+# The number of redirections to follow before giving up.
+# Note that only GET redirects are automatically followed.
+# Will also honor 301 requests by saving that info and never
+# requesting that URI again.
+DEFAULT_MAX_REDIRECTS = 5
+
+try:
+    # Users can optionally provide a module that tells us where the CA_CERTS
+    # are located.
+    import ca_certs_locater
+    CA_CERTS = ca_certs_locater.get()
+except ImportError:
+    # Default CA certificates file bundled with httplib2.
+    CA_CERTS = os.path.join(
+        os.path.dirname(os.path.abspath(__file__ )), "cacerts.txt")
+
+# Which headers are hop-by-hop headers by default
+HOP_BY_HOP = ['connection', 'keep-alive', 'proxy-authenticate', 'proxy-authorization', 'te', 'trailers', 'transfer-encoding', 'upgrade']
+
+def _get_end2end_headers(response):
+    hopbyhop = list(HOP_BY_HOP)
+    hopbyhop.extend([x.strip() for x in response.get('connection', '').split(',')])
+    return [header for header in response.keys() if header not in hopbyhop]
+
+URI = re.compile(r"^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?")
+
+def parse_uri(uri):
+    """Parses a URI using the regex given in Appendix B of RFC 3986.
+
+        (scheme, authority, path, query, fragment) = parse_uri(uri)
+    """
+    groups = URI.match(uri).groups()
+    return (groups[1], groups[3], groups[4], groups[6], groups[8])
+
+def urlnorm(uri):
+    (scheme, authority, path, query, fragment) = parse_uri(uri)
+    if not scheme or not authority:
+        raise RelativeURIError("Only absolute URIs are allowed. uri = %s" % uri)
+    authority = authority.lower()
+    scheme = scheme.lower()
+    if not path:
+        path = "/"
+    # Could do syntax based normalization of the URI before
+    # computing the digest. See Section 6.2.2 of Std 66.
+    request_uri = query and "?".join([path, query]) or path
+    scheme = scheme.lower()
+    defrag_uri = scheme + "://" + authority + request_uri
+    return scheme, authority, request_uri, defrag_uri
+
+
+# Cache filename construction (original borrowed from Venus http://intertwingly.net/code/venus/)
+re_url_scheme    = re.compile(r'^\w+://')
+re_slash         = re.compile(r'[?/:|]+')
+
+def safename(filename):
+    """Return a filename suitable for the cache.
+
+    Strips dangerous and common characters to create a filename we
+    can use to store the cache in.
+    """
+
+    try:
+        if re_url_scheme.match(filename):
+            if isinstance(filename,str):
+                filename = filename.decode('utf-8')
+                filename = filename.encode('idna')
+            else:
+                filename = filename.encode('idna')
+    except UnicodeError:
+        pass
+    if isinstance(filename,unicode):
+        filename=filename.encode('utf-8')
+    filemd5 = _md5(filename).hexdigest()
+    filename = re_url_scheme.sub("", filename)
+    filename = re_slash.sub(",", filename)
+
+    # limit length of filename
+    if len(filename)>200:
+        filename=filename[:200]
+    return ",".join((filename, filemd5))
+
+NORMALIZE_SPACE = re.compile(r'(?:\r\n)?[ \t]+')
+def _normalize_headers(headers):
+    return dict([ (key.lower(), NORMALIZE_SPACE.sub(value, ' ').strip())  for (key, value) in headers.iteritems()])
+
+def _parse_cache_control(headers):
+    retval = {}
+    if headers.has_key('cache-control'):
+        parts =  headers['cache-control'].split(',')
+        parts_with_args = [tuple([x.strip().lower() for x in part.split("=", 1)]) for part in parts if -1 != part.find("=")]
+        parts_wo_args = [(name.strip().lower(), 1) for name in parts if -1 == name.find("=")]
+        retval = dict(parts_with_args + parts_wo_args)
+    return retval
+
+# Whether to use a strict mode to parse WWW-Authenticate headers
+# Might lead to bad results in case of ill-formed header value,
+# so disabled by default, falling back to relaxed parsing.
+# Set to true to turn on, usefull for testing servers.
+USE_WWW_AUTH_STRICT_PARSING = 0
+
+# In regex below:
+#    [^\0-\x1f\x7f-\xff()<>@,;:\\\"/[\]?={} \t]+             matches a "token" as defined by HTTP
+#    "(?:[^\0-\x08\x0A-\x1f\x7f-\xff\\\"]|\\[\0-\x7f])*?"    matches a "quoted-string" as defined by HTTP, when LWS have already been replaced by a single space
+# Actually, as an auth-param value can be either a token or a quoted-string, they are combined in a single pattern which matches both:
+#    \"?((?<=\")(?:[^\0-\x1f\x7f-\xff\\\"]|\\[\0-\x7f])*?(?=\")|(?<!\")[^\0-\x08\x0A-\x1f\x7f-\xff()<>@,;:\\\"/[\]?={} \t]+(?!\"))\"?
+WWW_AUTH_STRICT = re.compile(r"^(?:\s*(?:,\s*)?([^\0-\x1f\x7f-\xff()<>@,;:\\\"/[\]?={} \t]+)\s*=\s*\"?((?<=\")(?:[^\0-\x08\x0A-\x1f\x7f-\xff\\\"]|\\[\0-\x7f])*?(?=\")|(?<!\")[^\0-\x1f\x7f-\xff()<>@,;:\\\"/[\]?={} \t]+(?!\"))\"?)(.*)$")
+WWW_AUTH_RELAXED = re.compile(r"^(?:\s*(?:,\s*)?([^ \t\r\n=]+)\s*=\s*\"?((?<=\")(?:[^\\\"]|\\.)*?(?=\")|(?<!\")[^ \t\r\n,]+(?!\"))\"?)(.*)$")
+UNQUOTE_PAIRS = re.compile(r'\\(.)')
+def _parse_www_authenticate(headers, headername='www-authenticate'):
+    """Returns a dictionary of dictionaries, one dict
+    per auth_scheme."""
+    retval = {}
+    if headers.has_key(headername):
+        try:
+
+            authenticate = headers[headername].strip()
+            www_auth = USE_WWW_AUTH_STRICT_PARSING and WWW_AUTH_STRICT or WWW_AUTH_RELAXED
+            while authenticate:
+                # Break off the scheme at the beginning of the line
+                if headername == 'authentication-info':
+                    (auth_scheme, the_rest) = ('digest', authenticate)
+                else:
+                    (auth_scheme, the_rest) = authenticate.split(" ", 1)
+                # Now loop over all the key value pairs that come after the scheme,
+                # being careful not to roll into the next scheme
+                match = www_auth.search(the_rest)
+                auth_params = {}
+                while match:
+                    if match and len(match.groups()) == 3:
+                        (key, value, the_rest) = match.groups()
+                        auth_params[key.lower()] = UNQUOTE_PAIRS.sub(r'\1', value) # '\\'.join([x.replace('\\', '') for x in value.split('\\\\')])
+                    match = www_auth.search(the_rest)
+                retval[auth_scheme.lower()] = auth_params
+                authenticate = the_rest.strip()
+
+        except ValueError:
+            raise MalformedHeader("WWW-Authenticate")
+    return retval
+
+
+def _entry_disposition(response_headers, request_headers):
+    """Determine freshness from the Date, Expires and Cache-Control headers.
+
+    We don't handle the following:
+
+    1. Cache-Control: max-stale
+    2. Age: headers are not used in the calculations.
+
+    Not that this algorithm is simpler than you might think
+    because we are operating as a private (non-shared) cache.
+    This lets us ignore 's-maxage'. We can also ignore
+    'proxy-invalidate' since we aren't a proxy.
+    We will never return a stale document as
+    fresh as a design decision, and thus the non-implementation
+    of 'max-stale'. This also lets us safely ignore 'must-revalidate'
+    since we operate as if every server has sent 'must-revalidate'.
+    Since we are private we get to ignore both 'public' and
+    'private' parameters. We also ignore 'no-transform' since
+    we don't do any transformations.
+    The 'no-store' parameter is handled at a higher level.
+    So the only Cache-Control parameters we look at are:
+
+    no-cache
+    only-if-cached
+    max-age
+    min-fresh
+    """
+
+    retval = "STALE"
+    cc = _parse_cache_control(request_headers)
+    cc_response = _parse_cache_control(response_headers)
+
+    if request_headers.has_key('pragma') and request_headers['pragma'].lower().find('no-cache') != -1:
+        retval = "TRANSPARENT"
+        if 'cache-control' not in request_headers:
+            request_headers['cache-control'] = 'no-cache'
+    elif cc.has_key('no-cache'):
+        retval = "TRANSPARENT"
+    elif cc_response.has_key('no-cache'):
+        retval = "STALE"
+    elif cc.has_key('only-if-cached'):
+        retval = "FRESH"
+    elif response_headers.has_key('date'):
+        date = calendar.timegm(email.Utils.parsedate_tz(response_headers['date']))
+        now = time.time()
+        current_age = max(0, now - date)
+        if cc_response.has_key('max-age'):
+            try:
+                freshness_lifetime = int(cc_response['max-age'])
+            except ValueError:
+                freshness_lifetime = 0
+        elif response_headers.has_key('expires'):
+            expires = email.Utils.parsedate_tz(response_headers['expires'])
+            if None == expires:
+                freshness_lifetime = 0
+            else:
+                freshness_lifetime = max(0, calendar.timegm(expires) - date)
+        else:
+            freshness_lifetime = 0
+        if cc.has_key('max-age'):
+            try:
+                freshness_lifetime = int(cc['max-age'])
+            except ValueError:
+                freshness_lifetime = 0
+        if cc.has_key('min-fresh'):
+            try:
+                min_fresh = int(cc['min-fresh'])
+            except ValueError:
+                min_fresh = 0
+            current_age += min_fresh
+        if freshness_lifetime > current_age:
+            retval = "FRESH"
+    return retval
+
+def _decompressContent(response, new_content):
+    content = new_content
+    try:
+        encoding = response.get('content-encoding', None)
+        if encoding in ['gzip', 'deflate']:
+            if encoding == 'gzip':
+                content = gzip.GzipFile(fileobj=StringIO.StringIO(new_content)).read()
+            if encoding == 'deflate':
+                content = zlib.decompress(content)
+            response['content-length'] = str(len(content))
+            # Record the historical presence of the encoding in a way the won't interfere.
+            response['-content-encoding'] = response['content-encoding']
+            del response['content-encoding']
+    except IOError:
+        content = ""
+        raise FailedToDecompressContent(_("Content purported to be compressed with %s but failed to decompress.") % response.get('content-encoding'), response, content)
+    return content
+
+def _updateCache(request_headers, response_headers, content, cache, cachekey):
+    if cachekey:
+        cc = _parse_cache_control(request_headers)
+        cc_response = _parse_cache_control(response_headers)
+        if cc.has_key('no-store') or cc_response.has_key('no-store'):
+            cache.delete(cachekey)
+        else:
+            info = email.Message.Message()
+            for key, value in response_headers.iteritems():
+                if key not in ['status','content-encoding','transfer-encoding']:
+                    info[key] = value
+
+            # Add annotations to the cache to indicate what headers
+            # are variant for this request.
+            vary = response_headers.get('vary', None)
+            if vary:
+                vary_headers = vary.lower().replace(' ', '').split(',')
+                for header in vary_headers:
+                    key = '-varied-%s' % header
+                    try:
+                        info[key] = request_headers[header]
+                    except KeyError:
+                        pass
+
+            status = response_headers.status
+            if status == 304:
+                status = 200
+
+            status_header = 'status: %d\r\n' % status
+
+            header_str = info.as_string()
+
+            header_str = re.sub("\r(?!\n)|(?<!\r)\n", "\r\n", header_str)
+            text = "".join([status_header, header_str, content])
+
+            cache.set(cachekey, text)
+
+def _cnonce():
+    dig = _md5("%s:%s" % (time.ctime(), ["0123456789"[random.randrange(0, 9)] for i in range(20)])).hexdigest()
+    return dig[:16]
+
+def _wsse_username_token(cnonce, iso_now, password):
+    return base64.b64encode(_sha("%s%s%s" % (cnonce, iso_now, password)).digest()).strip()
+
+
+# For credentials we need two things, first
+# a pool of credential to try (not necesarily tied to BAsic, Digest, etc.)
+# Then we also need a list of URIs that have already demanded authentication
+# That list is tricky since sub-URIs can take the same auth, or the
+# auth scheme may change as you descend the tree.
+# So we also need each Auth instance to be able to tell us
+# how close to the 'top' it is.
+
+class Authentication(object):
+    def __init__(self, credentials, host, request_uri, headers, response, content, http):
+        (scheme, authority, path, query, fragment) = parse_uri(request_uri)
+        self.path = path
+        self.host = host
+        self.credentials = credentials
+        self.http = http
+
+    def depth(self, request_uri):
+        (scheme, authority, path, query, fragment) = parse_uri(request_uri)
+        return request_uri[len(self.path):].count("/")
+
+    def inscope(self, host, request_uri):
+        # XXX Should we normalize the request_uri?
+        (scheme, authority, path, query, fragment) = parse_uri(request_uri)
+        return (host == self.host) and path.startswith(self.path)
+
+    def request(self, method, request_uri, headers, content):
+        """Modify the request headers to add the appropriate
+        Authorization header. Over-ride this in sub-classes."""
+        pass
+
+    def response(self, response, content):
+        """Gives us a chance to update with new nonces
+        or such returned from the last authorized response.
+        Over-rise this in sub-classes if necessary.
+
+        Return TRUE is the request is to be retried, for
+        example Digest may return stale=true.
+        """
+        return False
+
+
+
+class BasicAuthentication(Authentication):
+    def __init__(self, credentials, host, request_uri, headers, response, content, http):
+        Authentication.__init__(self, credentials, host, request_uri, headers, response, content, http)
+
+    def request(self, method, request_uri, headers, content):
+        """Modify the request headers to add the appropriate
+        Authorization header."""
+        headers['authorization'] = 'Basic ' + base64.b64encode("%s:%s" % self.credentials).strip()
+
+
+class DigestAuthentication(Authentication):
+    """Only do qop='auth' and MD5, since that
+    is all Apache currently implements"""
+    def __init__(self, credentials, host, request_uri, headers, response, content, http):
+        Authentication.__init__(self, credentials, host, request_uri, headers, response, content, http)
+        challenge = _parse_www_authenticate(response, 'www-authenticate')
+        self.challenge = challenge['digest']
+        qop = self.challenge.get('qop', 'auth')
+        self.challenge['qop'] = ('auth' in [x.strip() for x in qop.split()]) and 'auth' or None
+        if self.challenge['qop'] is None:
+            raise UnimplementedDigestAuthOptionError( _("Unsupported value for qop: %s." % qop))
+        self.challenge['algorithm'] = self.challenge.get('algorithm', 'MD5').upper()
+        if self.challenge['algorithm'] != 'MD5':
+            raise UnimplementedDigestAuthOptionError( _("Unsupported value for algorithm: %s." % self.challenge['algorithm']))
+        self.A1 = "".join([self.credentials[0], ":", self.challenge['realm'], ":", self.credentials[1]])
+        self.challenge['nc'] = 1
+
+    def request(self, method, request_uri, headers, content, cnonce = None):
+        """Modify the request headers"""
+        H = lambda x: _md5(x).hexdigest()
+        KD = lambda s, d: H("%s:%s" % (s, d))
+        A2 = "".join([method, ":", request_uri])
+        self.challenge['cnonce'] = cnonce or _cnonce()
+        request_digest  = '"%s"' % KD(H(self.A1), "%s:%s:%s:%s:%s" % (
+                self.challenge['nonce'],
+                '%08x' % self.challenge['nc'],
+                self.challenge['cnonce'],
+                self.challenge['qop'], H(A2)))
+        headers['authorization'] = 'Digest username="%s", realm="%s", nonce="%s", uri="%s", algorithm=%s, response=%s, qop=%s, nc=%08x, cnonce="%s"' % (
+                self.credentials[0],
+                self.challenge['realm'],
+                self.challenge['nonce'],
+                request_uri,
+                self.challenge['algorithm'],
+                request_digest,
+                self.challenge['qop'],
+                self.challenge['nc'],
+                self.challenge['cnonce'])
+        if self.challenge.get('opaque'):
+            headers['authorization'] += ', opaque="%s"' % self.challenge['opaque']
+        self.challenge['nc'] += 1
+
+    def response(self, response, content):
+        if not response.has_key('authentication-info'):
+            challenge = _parse_www_authenticate(response, 'www-authenticate').get('digest', {})
+            if 'true' == challenge.get('stale'):
+                self.challenge['nonce'] = challenge['nonce']
+                self.challenge['nc'] = 1
+                return True
+        else:
+            updated_challenge = _parse_www_authenticate(response, 'authentication-info').get('digest', {})
+
+            if updated_challenge.has_key('nextnonce'):
+                self.challenge['nonce'] = updated_challenge['nextnonce']
+                self.challenge['nc'] = 1
+        return False
+
+
+class HmacDigestAuthentication(Authentication):
+    """Adapted from Robert Sayre's code and DigestAuthentication above."""
+    __author__ = "Thomas Broyer (t.broyer@ltgt.net)"
+
+    def __init__(self, credentials, host, request_uri, headers, response, content, http):
+        Authentication.__init__(self, credentials, host, request_uri, headers, response, content, http)
+        challenge = _parse_www_authenticate(response, 'www-authenticate')
+        self.challenge = challenge['hmacdigest']
+        # TODO: self.challenge['domain']
+        self.challenge['reason'] = self.challenge.get('reason', 'unauthorized')
+        if self.challenge['reason'] not in ['unauthorized', 'integrity']:
+            self.challenge['reason'] = 'unauthorized'
+        self.challenge['salt'] = self.challenge.get('salt', '')
+        if not self.challenge.get('snonce'):
+            raise UnimplementedHmacDigestAuthOptionError( _("The challenge doesn't contain a server nonce, or this one is empty."))
+        self.challenge['algorithm'] = self.challenge.get('algorithm', 'HMAC-SHA-1')
+        if self.challenge['algorithm'] not in ['HMAC-SHA-1', 'HMAC-MD5']:
+            raise UnimplementedHmacDigestAuthOptionError( _("Unsupported value for algorithm: %s." % self.challenge['algorithm']))
+        self.challenge['pw-algorithm'] = self.challenge.get('pw-algorithm', 'SHA-1')
+        if self.challenge['pw-algorithm'] not in ['SHA-1', 'MD5']:
+            raise UnimplementedHmacDigestAuthOptionError( _("Unsupported value for pw-algorithm: %s." % self.challenge['pw-algorithm']))
+        if self.challenge['algorithm'] == 'HMAC-MD5':
+            self.hashmod = _md5
+        else:
+            self.hashmod = _sha
+        if self.challenge['pw-algorithm'] == 'MD5':
+            self.pwhashmod = _md5
+        else:
+            self.pwhashmod = _sha
+        self.key = "".join([self.credentials[0], ":",
+                            self.pwhashmod.new("".join([self.credentials[1], self.challenge['salt']])).hexdigest().lower(),
+                            ":", self.challenge['realm']])
+        self.key = self.pwhashmod.new(self.key).hexdigest().lower()
+
+    def request(self, method, request_uri, headers, content):
+        """Modify the request headers"""
+        keys = _get_end2end_headers(headers)
+        keylist = "".join(["%s " % k for k in keys])
+        headers_val = "".join([headers[k] for k in keys])
+        created = time.strftime('%Y-%m-%dT%H:%M:%SZ',time.gmtime())
+        cnonce = _cnonce()
+        request_digest = "%s:%s:%s:%s:%s" % (method, request_uri, cnonce, self.challenge['snonce'], headers_val)
+        request_digest  = hmac.new(self.key, request_digest, self.hashmod).hexdigest().lower()
+        headers['authorization'] = 'HMACDigest username="%s", realm="%s", snonce="%s", cnonce="%s", uri="%s", created="%s", response="%s", headers="%s"' % (
+                self.credentials[0],
+                self.challenge['realm'],
+                self.challenge['snonce'],
+                cnonce,
+                request_uri,
+                created,
+                request_digest,
+                keylist)
+
+    def response(self, response, content):
+        challenge = _parse_www_authenticate(response, 'www-authenticate').get('hmacdigest', {})
+        if challenge.get('reason') in ['integrity', 'stale']:
+            return True
+        return False
+
+
+class WsseAuthentication(Authentication):
+    """This is thinly tested and should not be relied upon.
+    At this time there isn't any third party server to test against.
+    Blogger and TypePad implemented this algorithm at one point
+    but Blogger has since switched to Basic over HTTPS and
+    TypePad has implemented it wrong, by never issuing a 401
+    challenge but instead requiring your client to telepathically know that
+    their endpoint is expecting WSSE profile="UsernameToken"."""
+    def __init__(self, credentials, host, request_uri, headers, response, content, http):
+        Authentication.__init__(self, credentials, host, request_uri, headers, response, content, http)
+
+    def request(self, method, request_uri, headers, content):
+        """Modify the request headers to add the appropriate
+        Authorization header."""
+        headers['authorization'] = 'WSSE profile="UsernameToken"'
+        iso_now = time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime())
+        cnonce = _cnonce()
+        password_digest = _wsse_username_token(cnonce, iso_now, self.credentials[1])
+        headers['X-WSSE'] = 'UsernameToken Username="%s", PasswordDigest="%s", Nonce="%s", Created="%s"' % (
+                self.credentials[0],
+                password_digest,
+                cnonce,
+                iso_now)
+
+class GoogleLoginAuthentication(Authentication):
+    def __init__(self, credentials, host, request_uri, headers, response, content, http):
+        from urllib import urlencode
+        Authentication.__init__(self, credentials, host, request_uri, headers, response, content, http)
+        challenge = _parse_www_authenticate(response, 'www-authenticate')
+        service = challenge['googlelogin'].get('service', 'xapi')
+        # Bloggger actually returns the service in the challenge
+        # For the rest we guess based on the URI
+        if service == 'xapi' and  request_uri.find("calendar") > 0:
+            service = "cl"
+        # No point in guessing Base or Spreadsheet
+        #elif request_uri.find("spreadsheets") > 0:
+        #    service = "wise"
+
+        auth = dict(Email=credentials[0], Passwd=credentials[1], service=service, source=headers['user-agent'])
+        resp, content = self.http.request("https://www.google.com/accounts/ClientLogin", method="POST", body=urlencode(auth), headers={'Content-Type': 'application/x-www-form-urlencoded'})
+        lines = content.split('\n')
+        d = dict([tuple(line.split("=", 1)) for line in lines if line])
+        if resp.status == 403:
+            self.Auth = ""
+        else:
+            self.Auth = d['Auth']
+
+    def request(self, method, request_uri, headers, content):
+        """Modify the request headers to add the appropriate
+        Authorization header."""
+        headers['authorization'] = 'GoogleLogin Auth=' + self.Auth
+
+
+AUTH_SCHEME_CLASSES = {
+    "basic": BasicAuthentication,
+    "wsse": WsseAuthentication,
+    "digest": DigestAuthentication,
+    "hmacdigest": HmacDigestAuthentication,
+    "googlelogin": GoogleLoginAuthentication
+}
+
+AUTH_SCHEME_ORDER = ["hmacdigest", "googlelogin", "digest", "wsse", "basic"]
+
+class FileCache(object):
+    """Uses a local directory as a store for cached files.
+    Not really safe to use if multiple threads or processes are going to
+    be running on the same cache.
+    """
+    def __init__(self, cache, safe=safename): # use safe=lambda x: md5.new(x).hexdigest() for the old behavior
+        self.cache = cache
+        self.safe = safe
+        if not os.path.exists(cache):
+            os.makedirs(self.cache)
+
+    def get(self, key):
+        retval = None
+        cacheFullPath = os.path.join(self.cache, self.safe(key))
+        try:
+            f = file(cacheFullPath, "rb")
+            retval = f.read()
+            f.close()
+        except IOError:
+            pass
+        return retval
+
+    def set(self, key, value):
+        cacheFullPath = os.path.join(self.cache, self.safe(key))
+        f = file(cacheFullPath, "wb")
+        f.write(value)
+        f.close()
+
+    def delete(self, key):
+        cacheFullPath = os.path.join(self.cache, self.safe(key))
+        if os.path.exists(cacheFullPath):
+            os.remove(cacheFullPath)
+
+class Credentials(object):
+    def __init__(self):
+        self.credentials = []
+
+    def add(self, name, password, domain=""):
+        self.credentials.append((domain.lower(), name, password))
+
+    def clear(self):
+        self.credentials = []
+
+    def iter(self, domain):
+        for (cdomain, name, password) in self.credentials:
+            if cdomain == "" or domain == cdomain:
+                yield (name, password)
+
+class KeyCerts(Credentials):
+    """Identical to Credentials except that
+    name/password are mapped to key/cert."""
+    pass
+
+class AllHosts(object):
+    pass
+
+class ProxyInfo(object):
+    """Collect information required to use a proxy."""
+    bypass_hosts = ()
+
+    def __init__(self, proxy_type, proxy_host, proxy_port,
+                 proxy_rdns=None, proxy_user=None, proxy_pass=None):
+        """The parameter proxy_type must be set to one of socks.PROXY_TYPE_XXX
+        constants. For example:
+
+        p = ProxyInfo(proxy_type=socks.PROXY_TYPE_HTTP,
+            proxy_host='localhost', proxy_port=8000)
+        """
+        self.proxy_type = proxy_type
+        self.proxy_host = proxy_host
+        self.proxy_port = proxy_port
+        self.proxy_rdns = proxy_rdns
+        self.proxy_user = proxy_user
+        self.proxy_pass = proxy_pass
+
+    def astuple(self):
+        return (self.proxy_type, self.proxy_host, self.proxy_port,
+                self.proxy_rdns, self.proxy_user, self.proxy_pass)
+
+    def isgood(self):
+        return (self.proxy_host != None) and (self.proxy_port != None)
+
+    def applies_to(self, hostname):
+        return not self.bypass_host(hostname)
+
+    def bypass_host(self, hostname):
+        """Has this host been excluded from the proxy config"""
+        if self.bypass_hosts is AllHosts:
+            return True
+
+        bypass = False
+        for domain in self.bypass_hosts:
+            if hostname.endswith(domain):
+                bypass = True
+
+        return bypass
+
+
+def proxy_info_from_environment(method='http'):
+    """
+    Read proxy info from the environment variables.
+    """
+    if method not in ['http', 'https']:
+        return
+
+    env_var = method + '_proxy'
+    url = os.environ.get(env_var, os.environ.get(env_var.upper()))
+    if not url:
+        return
+    pi = proxy_info_from_url(url, method)
+
+    no_proxy = os.environ.get('no_proxy', os.environ.get('NO_PROXY', ''))
+    bypass_hosts = []
+    if no_proxy:
+        bypass_hosts = no_proxy.split(',')
+    # special case, no_proxy=* means all hosts bypassed
+    if no_proxy == '*':
+        bypass_hosts = AllHosts
+
+    pi.bypass_hosts = bypass_hosts
+    return pi
+
+def proxy_info_from_url(url, method='http'):
+    """
+    Construct a ProxyInfo from a URL (such as http_proxy env var)
+    """
+    url = urlparse.urlparse(url)
+    username = None
+    password = None
+    port = None
+    if '@' in url[1]:
+        ident, host_port = url[1].split('@', 1)
+        if ':' in ident:
+            username, password = ident.split(':', 1)
+        else:
+            password = ident
+    else:
+        host_port = url[1]
+    if ':' in host_port:
+        host, port = host_port.split(':', 1)
+    else:
+        host = host_port
+
+    if port:
+        port = int(port)
+    else:
+        port = dict(https=443, http=80)[method]
+
+    proxy_type = 3 # socks.PROXY_TYPE_HTTP
+    return ProxyInfo(
+        proxy_type = proxy_type,
+        proxy_host = host,
+        proxy_port = port,
+        proxy_user = username or None,
+        proxy_pass = password or None,
+    )
+
+
+class HTTPConnectionWithTimeout(httplib.HTTPConnection):
+    """
+    HTTPConnection subclass that supports timeouts
+
+    All timeouts are in seconds. If None is passed for timeout then
+    Python's default timeout for sockets will be used. See for example
+    the docs of socket.setdefaulttimeout():
+    http://docs.python.org/library/socket.html#socket.setdefaulttimeout
+    """
+
+    def __init__(self, host, port=None, strict=None, timeout=None, proxy_info=None):
+        httplib.HTTPConnection.__init__(self, host, port, strict)
+        self.timeout = timeout
+        self.proxy_info = proxy_info
+
+    def connect(self):
+        """Connect to the host and port specified in __init__."""
+        # Mostly verbatim from httplib.py.
+        if self.proxy_info and socks is None:
+            raise ProxiesUnavailableError(
+                'Proxy support missing but proxy use was requested!')
+        msg = "getaddrinfo returns an empty list"
+        if self.proxy_info and self.proxy_info.isgood():
+            use_proxy = True
+            proxy_type, proxy_host, proxy_port, proxy_rdns, proxy_user, proxy_pass = self.proxy_info.astuple()
+        else:
+            use_proxy = False
+        if use_proxy and proxy_rdns:
+            host = proxy_host
+            port = proxy_port
+        else:
+            host = self.host
+            port = self.port
+
+        for res in socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM):
+            af, socktype, proto, canonname, sa = res
+            try:
+                if use_proxy:
+                    self.sock = socks.socksocket(af, socktype, proto)
+                    self.sock.setproxy(proxy_type, proxy_host, proxy_port, proxy_rdns, proxy_user, proxy_pass)
+                else:
+                    self.sock = socket.socket(af, socktype, proto)
+                    self.sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
+                # Different from httplib: support timeouts.
+                if has_timeout(self.timeout):
+                    self.sock.settimeout(self.timeout)
+                    # End of difference from httplib.
+                if self.debuglevel > 0:
+                    print "connect: (%s, %s) ************" % (self.host, self.port)
+                    if use_proxy:
+                        print "proxy: %s ************" % str((proxy_host, proxy_port, proxy_rdns, proxy_user, proxy_pass))
+
+                self.sock.connect((self.host, self.port) + sa[2:])
+            except socket.error, msg:
+                if self.debuglevel > 0:
+                    print "connect fail: (%s, %s)" % (self.host, self.port)
+                    if use_proxy:
+                        print "proxy: %s" % str((proxy_host, proxy_port, proxy_rdns, proxy_user, proxy_pass))
+                if self.sock:
+                    self.sock.close()
+                self.sock = None
+                continue
+            break
+        if not self.sock:
+            raise socket.error, msg
+
+class HTTPSConnectionWithTimeout(httplib.HTTPSConnection):
+    """
+    This class allows communication via SSL.
+
+    All timeouts are in seconds. If None is passed for timeout then
+    Python's default timeout for sockets will be used. See for example
+    the docs of socket.setdefaulttimeout():
+    http://docs.python.org/library/socket.html#socket.setdefaulttimeout
+    """
+    def __init__(self, host, port=None, key_file=None, cert_file=None,
+                 strict=None, timeout=None, proxy_info=None,
+                 ca_certs=None, disable_ssl_certificate_validation=False):
+        httplib.HTTPSConnection.__init__(self, host, port=port,
+                                         key_file=key_file,
+                                         cert_file=cert_file, strict=strict)
+        self.timeout = timeout
+        self.proxy_info = proxy_info
+        if ca_certs is None:
+            ca_certs = CA_CERTS
+        self.ca_certs = ca_certs
+        self.disable_ssl_certificate_validation = \
+                disable_ssl_certificate_validation
+
+    # The following two methods were adapted from https_wrapper.py, released
+    # with the Google Appengine SDK at
+    # http://googleappengine.googlecode.com/svn-history/r136/trunk/python/google/appengine/tools/https_wrapper.py
+    # under the following license:
+    #
+    # Copyright 2007 Google Inc.
+    #
+    # Licensed under the Apache License, Version 2.0 (the "License");
+    # you may not use this file except in compliance with the License.
+    # You may obtain a copy of the License at
+    #
+    #     http://www.apache.org/licenses/LICENSE-2.0
+    #
+    # Unless required by applicable law or agreed to in writing, software
+    # distributed under the License is distributed on an "AS IS" BASIS,
+    # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+    # See the License for the specific language governing permissions and
+    # limitations under the License.
+    #
+
+    def _GetValidHostsForCert(self, cert):
+        """Returns a list of valid host globs for an SSL certificate.
+
+        Args:
+          cert: A dictionary representing an SSL certificate.
+        Returns:
+          list: A list of valid host globs.
+        """
+        if 'subjectAltName' in cert:
+            return [x[1] for x in cert['subjectAltName']
+                    if x[0].lower() == 'dns']
+        else:
+            return [x[0][1] for x in cert['subject']
+                    if x[0][0].lower() == 'commonname']
+
+    def _ValidateCertificateHostname(self, cert, hostname):
+        """Validates that a given hostname is valid for an SSL certificate.
+
+        Args:
+          cert: A dictionary representing an SSL certificate.
+          hostname: The hostname to test.
+        Returns:
+          bool: Whether or not the hostname is valid for this certificate.
+        """
+        hosts = self._GetValidHostsForCert(cert)
+        for host in hosts:
+            host_re = host.replace('.', '\.').replace('*', '[^.]*')
+            if re.search('^%s$' % (host_re,), hostname, re.I):
+                return True
+        return False
+
+    def connect(self):
+        "Connect to a host on a given (SSL) port."
+
+        msg = "getaddrinfo returns an empty list"
+        if self.proxy_info and self.proxy_info.isgood():
+            use_proxy = True
+            proxy_type, proxy_host, proxy_port, proxy_rdns, proxy_user, proxy_pass = self.proxy_info.astuple()
+        else:
+            use_proxy = False
+        if use_proxy and proxy_rdns:
+            host = proxy_host
+            port = proxy_port
+        else:
+            host = self.host
+            port = self.port
+
+        address_info = socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM)
+        for family, socktype, proto, canonname, sockaddr in address_info:
+            try:
+                if use_proxy:
+                    sock = socks.socksocket(family, socktype, proto)
+
+                    sock.setproxy(proxy_type, proxy_host, proxy_port, proxy_rdns, proxy_user, proxy_pass)
+                else:
+                    sock = socket.socket(family, socktype, proto)
+                    sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
+
+                if has_timeout(self.timeout):
+                    sock.settimeout(self.timeout)
+                sock.connect((self.host, self.port))
+                self.sock =_ssl_wrap_socket(
+                    sock, self.key_file, self.cert_file,
+                    self.disable_ssl_certificate_validation, self.ca_certs)
+                if self.debuglevel > 0:
+                    print "connect: (%s, %s)" % (self.host, self.port)
+                    if use_proxy:
+                        print "proxy: %s" % str((proxy_host, proxy_port, proxy_rdns, proxy_user, proxy_pass))
+                if not self.disable_ssl_certificate_validation:
+                    cert = self.sock.getpeercert()
+                    hostname = self.host.split(':', 0)[0]
+                    if not self._ValidateCertificateHostname(cert, hostname):
+                        raise CertificateHostnameMismatch(
+                            'Server presented certificate that does not match '
+                            'host %s: %s' % (hostname, cert), hostname, cert)
+            except ssl_SSLError, e:
+                if sock:
+                    sock.close()
+                if self.sock:
+                    self.sock.close()
+                self.sock = None
+                # Unfortunately the ssl module doesn't seem to provide any way
+                # to get at more detailed error information, in particular
+                # whether the error is due to certificate validation or
+                # something else (such as SSL protocol mismatch).
+                if e.errno == ssl.SSL_ERROR_SSL:
+                    raise SSLHandshakeError(e)
+                else:
+                    raise
+            except (socket.timeout, socket.gaierror):
+                raise
+            except socket.error, msg:
+                if self.debuglevel > 0:
+                    print "connect fail: (%s, %s)" % (self.host, self.port)
+                    if use_proxy:
+                        print "proxy: %s" % str((proxy_host, proxy_port, proxy_rdns, proxy_user, proxy_pass))
+                if self.sock:
+                    self.sock.close()
+                self.sock = None
+                continue
+            break
+        if not self.sock:
+            raise socket.error, msg
+
+SCHEME_TO_CONNECTION = {
+    'http': HTTPConnectionWithTimeout,
+    'https': HTTPSConnectionWithTimeout
+}
+
+# Use a different connection object for Google App Engine
+try:
+    try:
+        from google.appengine.api import apiproxy_stub_map
+        if apiproxy_stub_map.apiproxy.GetStub('urlfetch') is None:
+            raise ImportError  # Bail out; we're not actually running on App Engine.
+        from google.appengine.api.urlfetch import fetch
+        from google.appengine.api.urlfetch import InvalidURLError
+    except (ImportError, AttributeError):
+        from google3.apphosting.api import apiproxy_stub_map
+        if apiproxy_stub_map.apiproxy.GetStub('urlfetch') is None:
+            raise ImportError  # Bail out; we're not actually running on App Engine.
+        from google3.apphosting.api.urlfetch import fetch
+        from google3.apphosting.api.urlfetch import InvalidURLError
+
+    def _new_fixed_fetch(validate_certificate):
+        def fixed_fetch(url, payload=None, method="GET", headers={},
+                        allow_truncated=False, follow_redirects=True,
+                        deadline=None):
+            if deadline is None:
+                deadline = socket.getdefaulttimeout() or 5
+            return fetch(url, payload=payload, method=method, headers=headers,
+                         allow_truncated=allow_truncated,
+                         follow_redirects=follow_redirects, deadline=deadline,
+                         validate_certificate=validate_certificate)
+        return fixed_fetch
+
+    class AppEngineHttpConnection(httplib.HTTPConnection):
+        """Use httplib on App Engine, but compensate for its weirdness.
+
+        The parameters key_file, cert_file, proxy_info, ca_certs, and
+        disable_ssl_certificate_validation are all dropped on the ground.
+        """
+        def __init__(self, host, port=None, key_file=None, cert_file=None,
+                     strict=None, timeout=None, proxy_info=None, ca_certs=None,
+                     disable_ssl_certificate_validation=False):
+            httplib.HTTPConnection.__init__(self, host, port=port,
+                                            strict=strict, timeout=timeout)
+
+    class AppEngineHttpsConnection(httplib.HTTPSConnection):
+        """Same as AppEngineHttpConnection, but for HTTPS URIs."""
+        def __init__(self, host, port=None, key_file=None, cert_file=None,
+                     strict=None, timeout=None, proxy_info=None, ca_certs=None,
+                     disable_ssl_certificate_validation=False):
+            httplib.HTTPSConnection.__init__(self, host, port=port,
+                                             key_file=key_file,
+                                             cert_file=cert_file, strict=strict,
+                                             timeout=timeout)
+            self._fetch = _new_fixed_fetch(
+                    not disable_ssl_certificate_validation)
+
+    # Update the connection classes to use the Googel App Engine specific ones.
+    SCHEME_TO_CONNECTION = {
+        'http': AppEngineHttpConnection,
+        'https': AppEngineHttpsConnection
+    }
+except (ImportError, AttributeError):
+    pass
+
+
+class Http(object):
+    """An HTTP client that handles:
+
+    - all methods
+    - caching
+    - ETags
+    - compression,
+    - HTTPS
+    - Basic
+    - Digest
+    - WSSE
+
+    and more.
+    """
+    def __init__(self, cache=None, timeout=None,
+                 proxy_info=proxy_info_from_environment,
+                 ca_certs=None, disable_ssl_certificate_validation=False):
+        """If 'cache' is a string then it is used as a directory name for
+        a disk cache. Otherwise it must be an object that supports the
+        same interface as FileCache.
+
+        All timeouts are in seconds. If None is passed for timeout
+        then Python's default timeout for sockets will be used. See
+        for example the docs of socket.setdefaulttimeout():
+        http://docs.python.org/library/socket.html#socket.setdefaulttimeout
+
+        `proxy_info` may be:
+          - a callable that takes the http scheme ('http' or 'https') and
+            returns a ProxyInfo instance per request. By default, uses
+            proxy_nfo_from_environment.
+          - a ProxyInfo instance (static proxy config).
+          - None (proxy disabled).
+
+        ca_certs is the path of a file containing root CA certificates for SSL
+        server certificate validation.  By default, a CA cert file bundled with
+        httplib2 is used.
+
+        If disable_ssl_certificate_validation is true, SSL cert validation will
+        not be performed.
+        """
+        self.proxy_info = proxy_info
+        self.ca_certs = ca_certs
+        self.disable_ssl_certificate_validation = \
+                disable_ssl_certificate_validation
+
+        # Map domain name to an httplib connection
+        self.connections = {}
+        # The location of the cache, for now a directory
+        # where cached responses are held.
+        if cache and isinstance(cache, basestring):
+            self.cache = FileCache(cache)
+        else:
+            self.cache = cache
+
+        # Name/password
+        self.credentials = Credentials()
+
+        # Key/cert
+        self.certificates = KeyCerts()
+
+        # authorization objects
+        self.authorizations = []
+
+        # If set to False then no redirects are followed, even safe ones.
+        self.follow_redirects = True
+
+        # Which HTTP methods do we apply optimistic concurrency to, i.e.
+        # which methods get an "if-match:" etag header added to them.
+        self.optimistic_concurrency_methods = ["PUT", "PATCH"]
+
+        # If 'follow_redirects' is True, and this is set to True then
+        # all redirecs are followed, including unsafe ones.
+        self.follow_all_redirects = False
+
+        self.ignore_etag = False
+
+        self.force_exception_to_status_code = False
+
+        self.timeout = timeout
+
+        # Keep Authorization: headers on a redirect.
+        self.forward_authorization_headers = False
+
+    def __getstate__(self):
+        state_dict = copy.copy(self.__dict__)
+        # In case request is augmented by some foreign object such as
+        # credentials which handle auth
+        if 'request' in state_dict:
+            del state_dict['request']
+        if 'connections' in state_dict:
+            del state_dict['connections']
+        return state_dict
+
+    def __setstate__(self, state):
+        self.__dict__.update(state)
+        self.connections = {}
+
+    def _auth_from_challenge(self, host, request_uri, headers, response, content):
+        """A generator that creates Authorization objects
+           that can be applied to requests.
+        """
+        challenges = _parse_www_authenticate(response, 'www-authenticate')
+        for cred in self.credentials.iter(host):
+            for scheme in AUTH_SCHEME_ORDER:
+                if challenges.has_key(scheme):
+                    yield AUTH_SCHEME_CLASSES[scheme](cred, host, request_uri, headers, response, content, self)
+
+    def add_credentials(self, name, password, domain=""):
+        """Add a name and password that will be used
+        any time a request requires authentication."""
+        self.credentials.add(name, password, domain)
+
+    def add_certificate(self, key, cert, domain):
+        """Add a key and cert that will be used
+        any time a request requires authentication."""
+        self.certificates.add(key, cert, domain)
+
+    def clear_credentials(self):
+        """Remove all the names and passwords
+        that are used for authentication"""
+        self.credentials.clear()
+        self.authorizations = []
+
+    def _conn_request(self, conn, request_uri, method, body, headers):
+        i = 0
+        seen_bad_status_line = False
+        while i < RETRIES:
+            i += 1
+            try:
+                if hasattr(conn, 'sock') and conn.sock is None:
+                    conn.connect()
+                conn.request(method, request_uri, body, headers)
+            except socket.timeout:
+                raise
+            except socket.gaierror:
+                conn.close()
+                raise ServerNotFoundError("Unable to find the server at %s" % conn.host)
+            except ssl_SSLError:
+                conn.close()
+                raise
+            except socket.error, e:
+                err = 0
+                if hasattr(e, 'args'):
+                    err = getattr(e, 'args')[0]
+                else:
+                    err = e.errno
+                if err == errno.ECONNREFUSED: # Connection refused
+                    raise
+            except httplib.HTTPException:
+                # Just because the server closed the connection doesn't apparently mean
+                # that the server didn't send a response.
+                if hasattr(conn, 'sock') and conn.sock is None:
+                    if i < RETRIES-1:
+                        conn.close()
+                        conn.connect()
+                        continue
+                    else:
+                        conn.close()
+                        raise
+                if i < RETRIES-1:
+                    conn.close()
+                    conn.connect()
+                    continue
+            try:
+                response = conn.getresponse()
+            except httplib.BadStatusLine:
+                # If we get a BadStatusLine on the first try then that means
+                # the connection just went stale, so retry regardless of the
+                # number of RETRIES set.
+                if not seen_bad_status_line and i == 1:
+                    i = 0
+                    seen_bad_status_line = True
+                    conn.close()
+                    conn.connect()
+                    continue
+                else:
+                    conn.close()
+                    raise
+            except (socket.error, httplib.HTTPException):
+                if i < RETRIES-1:
+                    conn.close()
+                    conn.connect()
+                    continue
+                else:
+                    conn.close()
+                    raise
+            else:
+                content = ""
+                if method == "HEAD":
+                    conn.close()
+                else:
+                    content = response.read()
+                response = Response(response)
+                if method != "HEAD":
+                    content = _decompressContent(response, content)
+            break
+        return (response, content)
+
+
+    def _request(self, conn, host, absolute_uri, request_uri, method, body, headers, redirections, cachekey):
+        """Do the actual request using the connection object
+        and also follow one level of redirects if necessary"""
+
+        auths = [(auth.depth(request_uri), auth) for auth in self.authorizations if auth.inscope(host, request_uri)]
+        auth = auths and sorted(auths)[0][1] or None
+        if auth:
+            auth.request(method, request_uri, headers, body)
+
+        (response, content) = self._conn_request(conn, request_uri, method, body, headers)
+
+        if auth:
+            if auth.response(response, body):
+                auth.request(method, request_uri, headers, body)
+                (response, content) = self._conn_request(conn, request_uri, method, body, headers )
+                response._stale_digest = 1
+
+        if response.status == 401:
+            for authorization in self._auth_from_challenge(host, request_uri, headers, response, content):
+                authorization.request(method, request_uri, headers, body)
+                (response, content) = self._conn_request(conn, request_uri, method, body, headers, )
+                if response.status != 401:
+                    self.authorizations.append(authorization)
+                    authorization.response(response, body)
+                    break
+
+        if (self.follow_all_redirects or (method in ["GET", "HEAD"]) or response.status == 303):
+            if self.follow_redirects and response.status in [300, 301, 302, 303, 307]:
+                # Pick out the location header and basically start from the beginning
+                # remembering first to strip the ETag header and decrement our 'depth'
+                if redirections:
+                    if not response.has_key('location') and response.status != 300:
+                        raise RedirectMissingLocation( _("Redirected but the response is missing a Location: header."), response, content)
+                    # Fix-up relative redirects (which violate an RFC 2616 MUST)
+                    if response.has_key('location'):
+                        location = response['location']
+                        (scheme, authority, path, query, fragment) = parse_uri(location)
+                        if authority == None:
+                            response['location'] = urlparse.urljoin(absolute_uri, location)
+                    if response.status == 301 and method in ["GET", "HEAD"]:
+                        response['-x-permanent-redirect-url'] = response['location']
+                        if not response.has_key('content-location'):
+                            response['content-location'] = absolute_uri
+                        _updateCache(headers, response, content, self.cache, cachekey)
+                    if headers.has_key('if-none-match'):
+                        del headers['if-none-match']
+                    if headers.has_key('if-modified-since'):
+                        del headers['if-modified-since']
+                    if 'authorization' in headers and not self.forward_authorization_headers:
+                        del headers['authorization']
+                    if response.has_key('location'):
+                        location = response['location']
+                        old_response = copy.deepcopy(response)
+                        if not old_response.has_key('content-location'):
+                            old_response['content-location'] = absolute_uri
+                        redirect_method = method
+                        if response.status in [302, 303]:
+                            redirect_method = "GET"
+                            body = None
+                        (response, content) = self.request(
+                            location, method=redirect_method,
+                            body=body, headers=headers,
+                            redirections=redirections - 1)
+                        response.previous = old_response
+                else:
+                    raise RedirectLimit("Redirected more times than rediection_limit allows.", response, content)
+            elif response.status in [200, 203] and method in ["GET", "HEAD"]:
+                # Don't cache 206's since we aren't going to handle byte range requests
+                if not response.has_key('content-location'):
+                    response['content-location'] = absolute_uri
+                _updateCache(headers, response, content, self.cache, cachekey)
+
+        return (response, content)
+
+    def _normalize_headers(self, headers):
+        return _normalize_headers(headers)
+
+# Need to catch and rebrand some exceptions
+# Then need to optionally turn all exceptions into status codes
+# including all socket.* and httplib.* exceptions.
+
+
+    def request(self, uri, method="GET", body=None, headers=None, redirections=DEFAULT_MAX_REDIRECTS, connection_type=None):
+        """ Performs a single HTTP request.
+
+        The 'uri' is the URI of the HTTP resource and can begin with either
+        'http' or 'https'. The value of 'uri' must be an absolute URI.
+
+        The 'method' is the HTTP method to perform, such as GET, POST, DELETE,
+        etc. There is no restriction on the methods allowed.
+
+        The 'body' is the entity body to be sent with the request. It is a
+        string object.
+
+        Any extra headers that are to be sent with the request should be
+        provided in the 'headers' dictionary.
+
+        The maximum number of redirect to follow before raising an
+        exception is 'redirections. The default is 5.
+
+        The return value is a tuple of (response, content), the first
+        being and instance of the 'Response' class, the second being
+        a string that contains the response entity body.
+        """
+        try:
+            if headers is None:
+                headers = {}
+            else:
+                headers = self._normalize_headers(headers)
+
+            if not headers.has_key('user-agent'):
+                headers['user-agent'] = "Python-httplib2/%s (gzip)" % __version__
+
+            uri = iri2uri(uri)
+
+            (scheme, authority, request_uri, defrag_uri) = urlnorm(uri)
+            domain_port = authority.split(":")[0:2]
+            if len(domain_port) == 2 and domain_port[1] == '443' and scheme == 'http':
+                scheme = 'https'
+                authority = domain_port[0]
+
+            proxy_info = self._get_proxy_info(scheme, authority)
+
+            conn_key = scheme+":"+authority
+            if conn_key in self.connections:
+                conn = self.connections[conn_key]
+            else:
+                if not connection_type:
+                    connection_type = SCHEME_TO_CONNECTION[scheme]
+                certs = list(self.certificates.iter(authority))
+                if scheme == 'https':
+                    if certs:
+                        conn = self.connections[conn_key] = connection_type(
+                                authority, key_file=certs[0][0],
+                                cert_file=certs[0][1], timeout=self.timeout,
+                                proxy_info=proxy_info,
+                                ca_certs=self.ca_certs,
+                                disable_ssl_certificate_validation=
+                                        self.disable_ssl_certificate_validation)
+                    else:
+                        conn = self.connections[conn_key] = connection_type(
+                                authority, timeout=self.timeout,
+                                proxy_info=proxy_info,
+                                ca_certs=self.ca_certs,
+                                disable_ssl_certificate_validation=
+                                        self.disable_ssl_certificate_validation)
+                else:
+                    conn = self.connections[conn_key] = connection_type(
+                            authority, timeout=self.timeout,
+                            proxy_info=proxy_info)
+                conn.set_debuglevel(debuglevel)
+
+            if 'range' not in headers and 'accept-encoding' not in headers:
+                headers['accept-encoding'] = 'gzip, deflate'
+
+            info = email.Message.Message()
+            cached_value = None
+            if self.cache:
+                cachekey = defrag_uri
+                cached_value = self.cache.get(cachekey)
+                if cached_value:
+                    # info = email.message_from_string(cached_value)
+                    #
+                    # Need to replace the line above with the kludge below
+                    # to fix the non-existent bug not fixed in this
+                    # bug report: http://mail.python.org/pipermail/python-bugs-list/2005-September/030289.html
+                    try:
+                        info, content = cached_value.split('\r\n\r\n', 1)
+                        feedparser = email.FeedParser.FeedParser()
+                        feedparser.feed(info)
+                        info = feedparser.close()
+                        feedparser._parse = None
+                    except (IndexError, ValueError):
+                        self.cache.delete(cachekey)
+                        cachekey = None
+                        cached_value = None
+            else:
+                cachekey = None
+
+            if method in self.optimistic_concurrency_methods and self.cache and info.has_key('etag') and not self.ignore_etag and 'if-match' not in headers:
+                # http://www.w3.org/1999/04/Editing/
+                headers['if-match'] = info['etag']
+
+            if method not in ["GET", "HEAD"] and self.cache and cachekey:
+                # RFC 2616 Section 13.10
+                self.cache.delete(cachekey)
+
+            # Check the vary header in the cache to see if this request
+            # matches what varies in the cache.
+            if method in ['GET', 'HEAD'] and 'vary' in info:
+                vary = info['vary']
+                vary_headers = vary.lower().replace(' ', '').split(',')
+                for header in vary_headers:
+                    key = '-varied-%s' % header
+                    value = info[key]
+                    if headers.get(header, None) != value:
+                        cached_value = None
+                        break
+
+            if cached_value and method in ["GET", "HEAD"] and self.cache and 'range' not in headers:
+                if info.has_key('-x-permanent-redirect-url'):
+                    # Should cached permanent redirects be counted in our redirection count? For now, yes.
+                    if redirections <= 0:
+                        raise RedirectLimit("Redirected more times than rediection_limit allows.", {}, "")
+                    (response, new_content) = self.request(
+                        info['-x-permanent-redirect-url'], method='GET',
+                        headers=headers, redirections=redirections - 1)
+                    response.previous = Response(info)
+                    response.previous.fromcache = True
+                else:
+                    # Determine our course of action:
+                    #   Is the cached entry fresh or stale?
+                    #   Has the client requested a non-cached response?
+                    #
+                    # There seems to be three possible answers:
+                    # 1. [FRESH] Return the cache entry w/o doing a GET
+                    # 2. [STALE] Do the GET (but add in cache validators if available)
+                    # 3. [TRANSPARENT] Do a GET w/o any cache validators (Cache-Control: no-cache) on the request
+                    entry_disposition = _entry_disposition(info, headers)
+
+                    if entry_disposition == "FRESH":
+                        if not cached_value:
+                            info['status'] = '504'
+                            content = ""
+                        response = Response(info)
+                        if cached_value:
+                            response.fromcache = True
+                        return (response, content)
+
+                    if entry_disposition == "STALE":
+                        if info.has_key('etag') and not self.ignore_etag and not 'if-none-match' in headers:
+                            headers['if-none-match'] = info['etag']
+                        if info.has_key('last-modified') and not 'last-modified' in headers:
+                            headers['if-modified-since'] = info['last-modified']
+                    elif entry_disposition == "TRANSPARENT":
+                        pass
+
+                    (response, new_content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey)
+
+                if response.status == 304 and method == "GET":
+                    # Rewrite the cache entry with the new end-to-end headers
+                    # Take all headers that are in response
+                    # and overwrite their values in info.
+                    # unless they are hop-by-hop, or are listed in the connection header.
+
+                    for key in _get_end2end_headers(response):
+                        info[key] = response[key]
+                    merged_response = Response(info)
+                    if hasattr(response, "_stale_digest"):
+                        merged_response._stale_digest = response._stale_digest
+                    _updateCache(headers, merged_response, content, self.cache, cachekey)
+                    response = merged_response
+                    response.status = 200
+                    response.fromcache = True
+
+                elif response.status == 200:
+                    content = new_content
+                else:
+                    self.cache.delete(cachekey)
+                    content = new_content
+            else:
+                cc = _parse_cache_control(headers)
+                if cc.has_key('only-if-cached'):
+                    info['status'] = '504'
+                    response = Response(info)
+                    content = ""
+                else:
+                    (response, content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey)
+        except Exception, e:
+            if self.force_exception_to_status_code:
+                if isinstance(e, HttpLib2ErrorWithResponse):
+                    response = e.response
+                    content = e.content
+                    response.status = 500
+                    response.reason = str(e)
+                elif isinstance(e, socket.timeout):
+                    content = "Request Timeout"
+                    response = Response({
+                        "content-type": "text/plain",
+                        "status": "408",
+                        "content-length": len(content)
+                    })
+                    response.reason = "Request Timeout"
+                else:
+                    content = str(e)
+                    response = Response({
+                        "content-type": "text/plain",
+                        "status": "400",
+                        "content-length": len(content)
+                    })
+                    response.reason = "Bad Request"
+            else:
+                raise
+
+
+        return (response, content)
+
+    def _get_proxy_info(self, scheme, authority):
+        """Return a ProxyInfo instance (or None) based on the scheme
+        and authority.
+        """
+        hostname, port = urllib.splitport(authority)
+        proxy_info = self.proxy_info
+        if callable(proxy_info):
+            proxy_info = proxy_info(scheme)
+
+        if (hasattr(proxy_info, 'applies_to')
+            and not proxy_info.applies_to(hostname)):
+            proxy_info = None
+        return proxy_info
+
+
+class Response(dict):
+    """An object more like email.Message than httplib.HTTPResponse."""
+
+    """Is this response from our local cache"""
+    fromcache = False
+
+    """HTTP protocol version used by server. 10 for HTTP/1.0, 11 for HTTP/1.1. """
+    version = 11
+
+    "Status code returned by server. "
+    status = 200
+
+    """Reason phrase returned by server."""
+    reason = "Ok"
+
+    previous = None
+
+    def __init__(self, info):
+        # info is either an email.Message or
+        # an httplib.HTTPResponse object.
+        if isinstance(info, httplib.HTTPResponse):
+            for key, value in info.getheaders():
+                self[key.lower()] = value
+            self.status = info.status
+            self['status'] = str(self.status)
+            self.reason = info.reason
+            self.version = info.version
+        elif isinstance(info, email.Message.Message):
+            for key, value in info.items():
+                self[key.lower()] = value
+            self.status = int(self['status'])
+        else:
+            for key, value in info.iteritems():
+                self[key.lower()] = value
+            self.status = int(self.get('status', self.status))
+            self.reason = self.get('reason', self.reason)
+
+
+    def __getattr__(self, name):
+        if name == 'dict':
+            return self
+        else:
+            raise AttributeError, name