Add google-endpoints to third_party/.

third_party/google-endpoints/urllib3/connectionpool.py

+from __future__ import absolute_import
+import errno
+import logging
+import sys
+import warnings
+
+from socket import error as SocketError, timeout as SocketTimeout
+import socket
+
+
+from .exceptions import (
+    ClosedPoolError,
+    ProtocolError,
+    EmptyPoolError,
+    HeaderParsingError,
+    HostChangedError,
+    LocationValueError,
+    MaxRetryError,
+    ProxyError,
+    ReadTimeoutError,
+    SSLError,
+    TimeoutError,
+    InsecureRequestWarning,
+    NewConnectionError,
+)
+from .packages.ssl_match_hostname import CertificateError
+from .packages import six
+from .packages.six.moves import queue
+from .connection import (
+    port_by_scheme,
+    DummyConnection,
+    HTTPConnection, HTTPSConnection, VerifiedHTTPSConnection,
+    HTTPException, BaseSSLError,
+)
+from .request import RequestMethods
+from .response import HTTPResponse
+
+from .util.connection import is_connection_dropped
+from .util.request import set_file_position
+from .util.response import assert_header_parsing
+from .util.retry import Retry
+from .util.timeout import Timeout
+from .util.url import get_host, Url
+
+
+if six.PY2:
+    # Queue is imported for side effects on MS Windows
+    import Queue as _unused_module_Queue  # noqa: F401
+
+xrange = six.moves.xrange
+
+log = logging.getLogger(__name__)
+
+_Default = object()
+
+
+# Pool objects
+class ConnectionPool(object):
+    """
+    Base class for all connection pools, such as
+    :class:`.HTTPConnectionPool` and :class:`.HTTPSConnectionPool`.
+    """
+
+    scheme = None
+    QueueCls = queue.LifoQueue
+
+    def __init__(self, host, port=None):
+        if not host:
+            raise LocationValueError("No host specified.")
+
+        self.host = _ipv6_host(host).lower()
+        self.port = port
+
+    def __str__(self):
+        return '%s(host=%r, port=%r)' % (type(self).__name__,
+                                         self.host, self.port)
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.close()
+        # Return False to re-raise any potential exceptions
+        return False
+
+    def close(self):
+        """
+        Close all pooled connections and disable the pool.
+        """
+        pass
+
+
+# This is taken from http://hg.python.org/cpython/file/7aaba721ebc0/Lib/socket.py#l252
+_blocking_errnos = set([errno.EAGAIN, errno.EWOULDBLOCK])
+
+
+class HTTPConnectionPool(ConnectionPool, RequestMethods):
+    """
+    Thread-safe connection pool for one host.
+
+    :param host:
+        Host used for this HTTP Connection (e.g. "localhost"), passed into
+        :class:`httplib.HTTPConnection`.
+
+    :param port:
+        Port used for this HTTP Connection (None is equivalent to 80), passed
+        into :class:`httplib.HTTPConnection`.
+
+    :param strict:
+        Causes BadStatusLine to be raised if the status line can't be parsed
+        as a valid HTTP/1.0 or 1.1 status line, passed into
+        :class:`httplib.HTTPConnection`.
+
+        .. note::
+           Only works in Python 2. This parameter is ignored in Python 3.
+
+    :param timeout:
+        Socket timeout in seconds for each individual connection. This can
+        be a float or integer, which sets the timeout for the HTTP request,
+        or an instance of :class:`urllib3.util.Timeout` which gives you more
+        fine-grained control over request timeouts. After the constructor has
+        been parsed, this is always a `urllib3.util.Timeout` object.
+
+    :param maxsize:
+        Number of connections to save that can be reused. More than 1 is useful
+        in multithreaded situations. If ``block`` is set to False, more
+        connections will be created but they will not be saved once they've
+        been used.
+
+    :param block:
+        If set to True, no more than ``maxsize`` connections will be used at
+        a time. When no free connections are available, the call will block
+        until a connection has been released. This is a useful side effect for
+        particular multithreaded situations where one does not want to use more
+        than maxsize connections per host to prevent flooding.
+
+    :param headers:
+        Headers to include with all requests, unless other headers are given
+        explicitly.
+
+    :param retries:
+        Retry configuration to use by default with requests in this pool.
+
+    :param _proxy:
+        Parsed proxy URL, should not be used directly, instead, see
+        :class:`urllib3.connectionpool.ProxyManager`"
+
+    :param _proxy_headers:
+        A dictionary with proxy headers, should not be used directly,
+        instead, see :class:`urllib3.connectionpool.ProxyManager`"
+
+    :param \\**conn_kw:
+        Additional parameters are used to create fresh :class:`urllib3.connection.HTTPConnection`,
+        :class:`urllib3.connection.HTTPSConnection` instances.
+    """
+
+    scheme = 'http'
+    ConnectionCls = HTTPConnection
+    ResponseCls = HTTPResponse
+
+    def __init__(self, host, port=None, strict=False,
+                 timeout=Timeout.DEFAULT_TIMEOUT, maxsize=1, block=False,
+                 headers=None, retries=None,
+                 _proxy=None, _proxy_headers=None,
+                 **conn_kw):
+        ConnectionPool.__init__(self, host, port)
+        RequestMethods.__init__(self, headers)
+
+        self.strict = strict
+
+        if not isinstance(timeout, Timeout):
+            timeout = Timeout.from_float(timeout)
+
+        if retries is None:
+            retries = Retry.DEFAULT
+
+        self.timeout = timeout
+        self.retries = retries
+
+        self.pool = self.QueueCls(maxsize)
+        self.block = block
+
+        self.proxy = _proxy
+        self.proxy_headers = _proxy_headers or {}
+
+        # Fill the queue up so that doing get() on it will block properly
+        for _ in xrange(maxsize):
+            self.pool.put(None)
+
+        # These are mostly for testing and debugging purposes.
+        self.num_connections = 0
+        self.num_requests = 0
+        self.conn_kw = conn_kw
+
+        if self.proxy:
+            # Enable Nagle's algorithm for proxies, to avoid packet fragmentation.
+            # We cannot know if the user has added default socket options, so we cannot replace the
+            # list.
+            self.conn_kw.setdefault('socket_options', [])
+
+    def _new_conn(self):
+        """
+        Return a fresh :class:`HTTPConnection`.
+        """
+        self.num_connections += 1
+        log.debug("Starting new HTTP connection (%d): %s",
+                  self.num_connections, self.host)
+
+        conn = self.ConnectionCls(host=self.host, port=self.port,
+                                  timeout=self.timeout.connect_timeout,
+                                  strict=self.strict, **self.conn_kw)
+        return conn
+
+    def _get_conn(self, timeout=None):
+        """
+        Get a connection. Will return a pooled connection if one is available.
+
+        If no connections are available and :prop:`.block` is ``False``, then a
+        fresh connection is returned.
+
+        :param timeout:
+            Seconds to wait before giving up and raising
+            :class:`urllib3.exceptions.EmptyPoolError` if the pool is empty and
+            :prop:`.block` is ``True``.
+        """
+        conn = None
+        try:
+            conn = self.pool.get(block=self.block, timeout=timeout)
+
+        except AttributeError:  # self.pool is None
+            raise ClosedPoolError(self, "Pool is closed.")
+
+        except queue.Empty:
+            if self.block:
+                raise EmptyPoolError(self,
+                                     "Pool reached maximum size and no more "
+                                     "connections are allowed.")
+            pass  # Oh well, we'll create a new connection then
+
+        # If this is a persistent connection, check if it got disconnected
+        if conn and is_connection_dropped(conn):
+            log.debug("Resetting dropped connection: %s", self.host)
+            conn.close()
+            if getattr(conn, 'auto_open', 1) == 0:
+                # This is a proxied connection that has been mutated by
+                # httplib._tunnel() and cannot be reused (since it would
+                # attempt to bypass the proxy)
+                conn = None
+
+        return conn or self._new_conn()
+
+    def _put_conn(self, conn):
+        """
+        Put a connection back into the pool.
+
+        :param conn:
+            Connection object for the current host and port as returned by
+            :meth:`._new_conn` or :meth:`._get_conn`.
+
+        If the pool is already full, the connection is closed and discarded
+        because we exceeded maxsize. If connections are discarded frequently,
+        then maxsize should be increased.
+
+        If the pool is closed, then the connection will be closed and discarded.
+        """
+        try:
+            self.pool.put(conn, block=False)
+            return  # Everything is dandy, done.
+        except AttributeError:
+            # self.pool is None.
+            pass
+        except queue.Full:
+            # This should never happen if self.block == True
+            log.warning(
+                "Connection pool is full, discarding connection: %s",
+                self.host)
+
+        # Connection never got put back into the pool, close it.
+        if conn:
+            conn.close()
+
+    def _validate_conn(self, conn):
+        """
+        Called right before a request is made, after the socket is created.
+        """
+        pass
+
+    def _prepare_proxy(self, conn):
+        # Nothing to do for HTTP connections.
+        pass
+
+    def _get_timeout(self, timeout):
+        """ Helper that always returns a :class:`urllib3.util.Timeout` """
+        if timeout is _Default:
+            return self.timeout.clone()
+
+        if isinstance(timeout, Timeout):
+            return timeout.clone()
+        else:
+            # User passed us an int/float. This is for backwards compatibility,
+            # can be removed later
+            return Timeout.from_float(timeout)
+
+    def _raise_timeout(self, err, url, timeout_value):
+        """Is the error actually a timeout? Will raise a ReadTimeout or pass"""
+
+        if isinstance(err, SocketTimeout):
+            raise ReadTimeoutError(self, url, "Read timed out. (read timeout=%s)" % timeout_value)
+
+        # See the above comment about EAGAIN in Python 3. In Python 2 we have
+        # to specifically catch it and throw the timeout error
+        if hasattr(err, 'errno') and err.errno in _blocking_errnos:
+            raise ReadTimeoutError(self, url, "Read timed out. (read timeout=%s)" % timeout_value)
+
+        # Catch possible read timeouts thrown as SSL errors. If not the
+        # case, rethrow the original. We need to do this because of:
+        # http://bugs.python.org/issue10272
+        if 'timed out' in str(err) or 'did not complete (read)' in str(err):  # Python 2.6
+            raise ReadTimeoutError(self, url, "Read timed out. (read timeout=%s)" % timeout_value)
+
+    def _make_request(self, conn, method, url, timeout=_Default, chunked=False,
+                      **httplib_request_kw):
+        """
+        Perform a request on a given urllib connection object taken from our
+        pool.
+
+        :param conn:
+            a connection from one of our connection pools
+
+        :param timeout:
+            Socket timeout in seconds for the request. This can be a
+            float or integer, which will set the same timeout value for
+            the socket connect and the socket read, or an instance of
+            :class:`urllib3.util.Timeout`, which gives you more fine-grained
+            control over your timeouts.
+        """
+        self.num_requests += 1
+
+        timeout_obj = self._get_timeout(timeout)
+        timeout_obj.start_connect()
+        conn.timeout = timeout_obj.connect_timeout
+
+        # Trigger any extra validation we need to do.
+        try:
+            self._validate_conn(conn)
+        except (SocketTimeout, BaseSSLError) as e:
+            # Py2 raises this as a BaseSSLError, Py3 raises it as socket timeout.
+            self._raise_timeout(err=e, url=url, timeout_value=conn.timeout)
+            raise
+
+        # conn.request() calls httplib.*.request, not the method in
+        # urllib3.request. It also calls makefile (recv) on the socket.
+        if chunked:
+            conn.request_chunked(method, url, **httplib_request_kw)
+        else:
+            conn.request(method, url, **httplib_request_kw)
+
+        # Reset the timeout for the recv() on the socket
+        read_timeout = timeout_obj.read_timeout
+
+        # App Engine doesn't have a sock attr
+        if getattr(conn, 'sock', None):
+            # In Python 3 socket.py will catch EAGAIN and return None when you
+            # try and read into the file pointer created by http.client, which
+            # instead raises a BadStatusLine exception. Instead of catching
+            # the exception and assuming all BadStatusLine exceptions are read
+            # timeouts, check for a zero timeout before making the request.
+            if read_timeout == 0:
+                raise ReadTimeoutError(
+                    self, url, "Read timed out. (read timeout=%s)" % read_timeout)
+            if read_timeout is Timeout.DEFAULT_TIMEOUT:
+                conn.sock.settimeout(socket.getdefaulttimeout())
+            else:  # None or a value
+                conn.sock.settimeout(read_timeout)
+
+        # Receive the response from the server
+        try:
+            try:  # Python 2.7, use buffering of HTTP responses
+                httplib_response = conn.getresponse(buffering=True)
+            except TypeError:  # Python 2.6 and older, Python 3
+                try:
+                    httplib_response = conn.getresponse()
+                except Exception as e:
+                    # Remove the TypeError from the exception chain in Python 3;
+                    # otherwise it looks like a programming error was the cause.
+                    six.raise_from(e, None)
+        except (SocketTimeout, BaseSSLError, SocketError) as e:
+            self._raise_timeout(err=e, url=url, timeout_value=read_timeout)
+            raise
+
+        # AppEngine doesn't have a version attr.
+        http_version = getattr(conn, '_http_vsn_str', 'HTTP/?')
+        log.debug("%s://%s:%s \"%s %s %s\" %s %s", self.scheme, self.host, self.port,
+                  method, url, http_version, httplib_response.status,
+                  httplib_response.length)
+
+        try:
+            assert_header_parsing(httplib_response.msg)
+        except HeaderParsingError as hpe:  # Platform-specific: Python 3
+            log.warning(
+                'Failed to parse headers (url=%s): %s',
+                self._absolute_url(url), hpe, exc_info=True)
+
+        return httplib_response
+
+    def _absolute_url(self, path):
+        return Url(scheme=self.scheme, host=self.host, port=self.port, path=path).url
+
+    def close(self):
+        """
+        Close all pooled connections and disable the pool.
+        """
+        # Disable access to the pool
+        old_pool, self.pool = self.pool, None
+
+        try:
+            while True:
+                conn = old_pool.get(block=False)
+                if conn:
+                    conn.close()
+
+        except queue.Empty:
+            pass  # Done.
+
+    def is_same_host(self, url):
+        """
+        Check if the given ``url`` is a member of the same host as this
+        connection pool.
+        """
+        if url.startswith('/'):
+            return True
+
+        # TODO: Add optional support for socket.gethostbyname checking.
+        scheme, host, port = get_host(url)
+
+        host = _ipv6_host(host).lower()
+
+        # Use explicit default port for comparison when none is given
+        if self.port and not port:
+            port = port_by_scheme.get(scheme)
+        elif not self.port and port == port_by_scheme.get(scheme):
+            port = None
+
+        return (scheme, host, port) == (self.scheme, self.host, self.port)
+
+    def urlopen(self, method, url, body=None, headers=None, retries=None,
+                redirect=True, assert_same_host=True, timeout=_Default,
+                pool_timeout=None, release_conn=None, chunked=False,
+                body_pos=None, **response_kw):
+        """
+        Get a connection from the pool and perform an HTTP request. This is the
+        lowest level call for making a request, so you'll need to specify all
+        the raw details.
+
+        .. note::
+
+           More commonly, it's appropriate to use a convenience method provided
+           by :class:`.RequestMethods`, such as :meth:`request`.
+
+        .. note::
+
+           `release_conn` will only behave as expected if
+           `preload_content=False` because we want to make
+           `preload_content=False` the default behaviour someday soon without
+           breaking backwards compatibility.
+
+        :param method:
+            HTTP request method (such as GET, POST, PUT, etc.)
+
+        :param body:
+            Data to send in the request body (useful for creating
+            POST requests, see HTTPConnectionPool.post_url for
+            more convenience).
+
+        :param headers:
+            Dictionary of custom headers to send, such as User-Agent,
+            If-None-Match, etc. If None, pool headers are used. If provided,
+            these headers completely replace any pool-specific headers.
+
+        :param retries:
+            Configure the number of retries to allow before raising a
+            :class:`~urllib3.exceptions.MaxRetryError` exception.
+
+            Pass ``None`` to retry until you receive a response. Pass a
+            :class:`~urllib3.util.retry.Retry` object for fine-grained control
+            over different types of retries.
+            Pass an integer number to retry connection errors that many times,
+            but no other types of errors. Pass zero to never retry.
+
+            If ``False``, then retries are disabled and any exception is raised
+            immediately. Also, instead of raising a MaxRetryError on redirects,
+            the redirect response will be returned.
+
+        :type retries: :class:`~urllib3.util.retry.Retry`, False, or an int.
+
+        :param redirect:
+            If True, automatically handle redirects (status codes 301, 302,
+            303, 307, 308). Each redirect counts as a retry. Disabling retries
+            will disable redirect, too.
+
+        :param assert_same_host:
+            If ``True``, will make sure that the host of the pool requests is
+            consistent else will raise HostChangedError. When False, you can
+            use the pool on an HTTP proxy and request foreign hosts.
+
+        :param timeout:
+            If specified, overrides the default timeout for this one
+            request. It may be a float (in seconds) or an instance of
+            :class:`urllib3.util.Timeout`.
+
+        :param pool_timeout:
+            If set and the pool is set to block=True, then this method will
+            block for ``pool_timeout`` seconds and raise EmptyPoolError if no
+            connection is available within the time period.
+
+        :param release_conn:
+            If False, then the urlopen call will not release the connection
+            back into the pool once a response is received (but will release if
+            you read the entire contents of the response such as when
+            `preload_content=True`). This is useful if you're not preloading
+            the response's content immediately. You will need to call
+            ``r.release_conn()`` on the response ``r`` to return the connection
+            back into the pool. If None, it takes the value of
+            ``response_kw.get('preload_content', True)``.
+
+        :param chunked:
+            If True, urllib3 will send the body using chunked transfer
+            encoding. Otherwise, urllib3 will send the body using the standard
+            content-length form. Defaults to False.
+
+        :param int body_pos:
+            Position to seek to in file-like body in the event of a retry or
+            redirect. Typically this won't need to be set because urllib3 will
+            auto-populate the value when needed.
+
+        :param \\**response_kw:
+            Additional parameters are passed to
+            :meth:`urllib3.response.HTTPResponse.from_httplib`
+        """
+        if headers is None:
+            headers = self.headers
+
+        if not isinstance(retries, Retry):
+            retries = Retry.from_int(retries, redirect=redirect, default=self.retries)
+
+        if release_conn is None:
+            release_conn = response_kw.get('preload_content', True)
+
+        # Check host
+        if assert_same_host and not self.is_same_host(url):
+            raise HostChangedError(self, url, retries)
+
+        conn = None
+
+        # Track whether `conn` needs to be released before
+        # returning/raising/recursing. Update this variable if necessary, and
+        # leave `release_conn` constant throughout the function. That way, if
+        # the function recurses, the original value of `release_conn` will be
+        # passed down into the recursive call, and its value will be respected.
+        #
+        # See issue #651 [1] for details.
+        #
+        # [1] <https://github.com/shazow/urllib3/issues/651>
+        release_this_conn = release_conn
+
+        # Merge the proxy headers. Only do this in HTTP. We have to copy the
+        # headers dict so we can safely change it without those changes being
+        # reflected in anyone else's copy.
+        if self.scheme == 'http':
+            headers = headers.copy()
+            headers.update(self.proxy_headers)
+
+        # Must keep the exception bound to a separate variable or else Python 3
+        # complains about UnboundLocalError.
+        err = None
+
+        # Keep track of whether we cleanly exited the except block. This
+        # ensures we do proper cleanup in finally.
+        clean_exit = False
+
+        # Rewind body position, if needed. Record current position
+        # for future rewinds in the event of a redirect/retry.
+        body_pos = set_file_position(body, body_pos)
+
+        try:
+            # Request a connection from the queue.
+            timeout_obj = self._get_timeout(timeout)
+            conn = self._get_conn(timeout=pool_timeout)
+
+            conn.timeout = timeout_obj.connect_timeout
+
+            is_new_proxy_conn = self.proxy is not None and not getattr(conn, 'sock', None)
+            if is_new_proxy_conn:
+                self._prepare_proxy(conn)
+
+            # Make the request on the httplib connection object.
+            httplib_response = self._make_request(conn, method, url,
+                                                  timeout=timeout_obj,
+                                                  body=body, headers=headers,
+                                                  chunked=chunked)
+
+            # If we're going to release the connection in ``finally:``, then
+            # the response doesn't need to know about the connection. Otherwise
+            # it will also try to release it and we'll have a double-release
+            # mess.
+            response_conn = conn if not release_conn else None
+
+            # Pass method to Response for length checking
+            response_kw['request_method'] = method
+
+            # Import httplib's response into our own wrapper object
+            response = self.ResponseCls.from_httplib(httplib_response,
+                                                     pool=self,
+                                                     connection=response_conn,
+                                                     retries=retries,
+                                                     **response_kw)
+
+            # Everything went great!
+            clean_exit = True
+
+        except queue.Empty:
+            # Timed out by queue.
+            raise EmptyPoolError(self, "No pool connections are available.")
+
+        except (BaseSSLError, CertificateError) as e:
+            # Close the connection. If a connection is reused on which there
+            # was a Certificate error, the next request will certainly raise
+            # another Certificate error.
+            clean_exit = False
+            raise SSLError(e)
+
+        except SSLError:
+            # Treat SSLError separately from BaseSSLError to preserve
+            # traceback.
+            clean_exit = False
+            raise
+
+        except (TimeoutError, HTTPException, SocketError, ProtocolError) as e:
+            # Discard the connection for these exceptions. It will be
+            # be replaced during the next _get_conn() call.
+            clean_exit = False
+
+            if isinstance(e, (SocketError, NewConnectionError)) and self.proxy:
+                e = ProxyError('Cannot connect to proxy.', e)
+            elif isinstance(e, (SocketError, HTTPException)):
+                e = ProtocolError('Connection aborted.', e)
+
+            retries = retries.increment(method, url, error=e, _pool=self,
+                                        _stacktrace=sys.exc_info()[2])
+            retries.sleep()
+
+            # Keep track of the error for the retry warning.
+            err = e
+
+        finally:
+            if not clean_exit:
+                # We hit some kind of exception, handled or otherwise. We need
+                # to throw the connection away unless explicitly told not to.
+                # Close the connection, set the variable to None, and make sure
+                # we put the None back in the pool to avoid leaking it.
+                conn = conn and conn.close()
+                release_this_conn = True
+
+            if release_this_conn:
+                # Put the connection back to be reused. If the connection is
+                # expired then it will be None, which will get replaced with a
+                # fresh connection during _get_conn.
+                self._put_conn(conn)
+
+        if not conn:
+            # Try again
+            log.warning("Retrying (%r) after connection "
+                        "broken by '%r': %s", retries, err, url)
+            return self.urlopen(method, url, body, headers, retries,
+                                redirect, assert_same_host,
+                                timeout=timeout, pool_timeout=pool_timeout,
+                                release_conn=release_conn, body_pos=body_pos,
+                                **response_kw)
+
+        # Handle redirect?
+        redirect_location = redirect and response.get_redirect_location()
+        if redirect_location:
+            if response.status == 303:
+                method = 'GET'
+
+            try:
+                retries = retries.increment(method, url, response=response, _pool=self)
+            except MaxRetryError:
+                if retries.raise_on_redirect:
+                    # Release the connection for this response, since we're not
+                    # returning it to be released manually.
+                    response.release_conn()
+                    raise
+                return response
+
+            retries.sleep_for_retry(response)
+            log.debug("Redirecting %s -> %s", url, redirect_location)
+            return self.urlopen(
+                method, redirect_location, body, headers,
+                retries=retries, redirect=redirect,
+                assert_same_host=assert_same_host,
+                timeout=timeout, pool_timeout=pool_timeout,
+                release_conn=release_conn, body_pos=body_pos,
+                **response_kw)
+
+        # Check if we should retry the HTTP response.
+        has_retry_after = bool(response.getheader('Retry-After'))
+        if retries.is_retry(method, response.status, has_retry_after):
+            try:
+                retries = retries.increment(method, url, response=response, _pool=self)
+            except MaxRetryError:
+                if retries.raise_on_status:
+                    # Release the connection for this response, since we're not
+                    # returning it to be released manually.
+                    response.release_conn()
+                    raise
+                return response
+            retries.sleep(response)
+            log.debug("Retry: %s", url)
+            return self.urlopen(
+                method, url, body, headers,
+                retries=retries, redirect=redirect,
+                assert_same_host=assert_same_host,
+                timeout=timeout, pool_timeout=pool_timeout,
+                release_conn=release_conn,
+                body_pos=body_pos, **response_kw)
+
+        return response
+
+
+class HTTPSConnectionPool(HTTPConnectionPool):
+    """
+    Same as :class:`.HTTPConnectionPool`, but HTTPS.
+
+    When Python is compiled with the :mod:`ssl` module, then
+    :class:`.VerifiedHTTPSConnection` is used, which *can* verify certificates,
+    instead of :class:`.HTTPSConnection`.
+
+    :class:`.VerifiedHTTPSConnection` uses one of ``assert_fingerprint``,
+    ``assert_hostname`` and ``host`` in this order to verify connections.
+    If ``assert_hostname`` is False, no verification is done.
+
+    The ``key_file``, ``cert_file``, ``cert_reqs``, ``ca_certs``,
+    ``ca_cert_dir``, and ``ssl_version`` are only used if :mod:`ssl` is
+    available and are fed into :meth:`urllib3.util.ssl_wrap_socket` to upgrade
+    the connection socket into an SSL socket.
+    """
+
+    scheme = 'https'
+    ConnectionCls = HTTPSConnection
+
+    def __init__(self, host, port=None,
+                 strict=False, timeout=Timeout.DEFAULT_TIMEOUT, maxsize=1,
+                 block=False, headers=None, retries=None,
+                 _proxy=None, _proxy_headers=None,
+                 key_file=None, cert_file=None, cert_reqs=None,
+                 ca_certs=None, ssl_version=None,
+                 assert_hostname=None, assert_fingerprint=None,
+                 ca_cert_dir=None, **conn_kw):
+
+        HTTPConnectionPool.__init__(self, host, port, strict, timeout, maxsize,
+                                    block, headers, retries, _proxy, _proxy_headers,
+                                    **conn_kw)
+
+        if ca_certs and cert_reqs is None:
+            cert_reqs = 'CERT_REQUIRED'
+
+        self.key_file = key_file
+        self.cert_file = cert_file
+        self.cert_reqs = cert_reqs
+        self.ca_certs = ca_certs
+        self.ca_cert_dir = ca_cert_dir
+        self.ssl_version = ssl_version
+        self.assert_hostname = assert_hostname
+        self.assert_fingerprint = assert_fingerprint
+
+    def _prepare_conn(self, conn):
+        """
+        Prepare the ``connection`` for :meth:`urllib3.util.ssl_wrap_socket`
+        and establish the tunnel if proxy is used.
+        """
+
+        if isinstance(conn, VerifiedHTTPSConnection):
+            conn.set_cert(key_file=self.key_file,
+                          cert_file=self.cert_file,
+                          cert_reqs=self.cert_reqs,
+                          ca_certs=self.ca_certs,
+                          ca_cert_dir=self.ca_cert_dir,
+                          assert_hostname=self.assert_hostname,
+                          assert_fingerprint=self.assert_fingerprint)
+            conn.ssl_version = self.ssl_version
+        return conn
+
+    def _prepare_proxy(self, conn):
+        """
+        Establish tunnel connection early, because otherwise httplib
+        would improperly set Host: header to proxy's IP:port.
+        """
+        # Python 2.7+
+        try:
+            set_tunnel = conn.set_tunnel
+        except AttributeError:  # Platform-specific: Python 2.6
+            set_tunnel = conn._set_tunnel
+
+        if sys.version_info <= (2, 6, 4) and not self.proxy_headers:  # Python 2.6.4 and older
+            set_tunnel(self.host, self.port)
+        else:
+            set_tunnel(self.host, self.port, self.proxy_headers)
+
+        conn.connect()
+
+    def _new_conn(self):
+        """
+        Return a fresh :class:`httplib.HTTPSConnection`.
+        """
+        self.num_connections += 1
+        log.debug("Starting new HTTPS connection (%d): %s",
+                  self.num_connections, self.host)
+
+        if not self.ConnectionCls or self.ConnectionCls is DummyConnection:
+            raise SSLError("Can't connect to HTTPS URL because the SSL "
+                           "module is not available.")
+
+        actual_host = self.host
+        actual_port = self.port
+        if self.proxy is not None:
+            actual_host = self.proxy.host
+            actual_port = self.proxy.port
+
+        conn = self.ConnectionCls(host=actual_host, port=actual_port,
+                                  timeout=self.timeout.connect_timeout,
+                                  strict=self.strict, **self.conn_kw)
+
+        return self._prepare_conn(conn)
+
+    def _validate_conn(self, conn):
+        """
+        Called right before a request is made, after the socket is created.
+        """
+        super(HTTPSConnectionPool, self)._validate_conn(conn)
+
+        # Force connect early to allow us to validate the connection.
+        if not getattr(conn, 'sock', None):  # AppEngine might not have  `.sock`
+            conn.connect()
+
+        if not conn.is_verified:
+            warnings.warn((
+                'Unverified HTTPS request is being made. '
+                'Adding certificate verification is strongly advised. See: '
+                'https://urllib3.readthedocs.io/en/latest/advanced-usage.html'
+                '#ssl-warnings'),
+                InsecureRequestWarning)
+
+
+def connection_from_url(url, **kw):
+    """
+    Given a url, return an :class:`.ConnectionPool` instance of its host.
+
+    This is a shortcut for not having to parse out the scheme, host, and port
+    of the url before creating an :class:`.ConnectionPool` instance.
+
+    :param url:
+        Absolute URL string that must include the scheme. Port is optional.
+
+    :param \\**kw:
+        Passes additional parameters to the constructor of the appropriate
+        :class:`.ConnectionPool`. Useful for specifying things like
+        timeout, maxsize, headers, etc.
+
+    Example::
+
+        >>> conn = connection_from_url('http://google.com/')
+        >>> r = conn.request('GET', '/')
+    """
+    scheme, host, port = get_host(url)
+    port = port or port_by_scheme.get(scheme, 80)
+    if scheme == 'https':
+        return HTTPSConnectionPool(host, port=port, **kw)
+    else:
+        return HTTPConnectionPool(host, port=port, **kw)
+
+
+def _ipv6_host(host):
+    """
+    Process IPv6 address literals
+    """
+
+    # httplib doesn't like it when we include brackets in IPv6 addresses
+    # Specifically, if we include brackets but also pass the port then
+    # httplib crazily doubles up the square brackets on the Host header.
+    # Instead, we need to make sure we never pass ``None`` as the port.
+    # However, for backward compatibility reasons we can't actually
+    # *assert* that.  See http://bugs.python.org/issue28539
+    #
+    # Also if an IPv6 address literal has a zone identifier, the
+    # percent sign might be URIencoded, convert it back into ASCII
+    if host.startswith('[') and host.endswith(']'):
+        host = host.replace('%25', '%').strip('[]')
+    return host