Revert "Use urllib for chunked requests"

This reverts commit 2da7fe0.

requests/adapters.py

@@ -435,19 +435,64 @@ def send(self, request, stream=False, timeout=None, verify=True, cert=None, prox
             timeout = TimeoutSauce(connect=timeout, read=timeout)
 
         try:
-            resp = conn.urlopen(
-                method=request.method,
-                url=url,
-                body=request.body,
-                headers=request.headers,
-                redirect=False,
-                assert_same_host=False,
-                preload_content=False,
-                decode_content=False,
-                retries=self.max_retries,
-                timeout=timeout,
-                chunked=chunked
-            )
+            if not chunked:
+                resp = conn.urlopen(
+                    method=request.method,
+                    url=url,
+                    body=request.body,
+                    headers=request.headers,
+                    redirect=False,
+                    assert_same_host=False,
+                    preload_content=False,
+                    decode_content=False,
+                    retries=self.max_retries,
+                    timeout=timeout
+                )
+
+            # Send the request.
+            else:
+                if hasattr(conn, 'proxy_pool'):
+                    conn = conn.proxy_pool
+
+                low_conn = conn._get_conn(timeout=DEFAULT_POOL_TIMEOUT)
+
+                try:
+                    low_conn.putrequest(request.method,
+                                        url,
+                                        skip_accept_encoding=True)
+
+                    for header, value in request.headers.items():
+                        low_conn.putheader(header, value)
+
+                    low_conn.endheaders()
+
+                    for i in request.body:
+                        low_conn.send(hex(len(i))[2:].encode('utf-8'))
+                        low_conn.send(b'\r\n')
+                        low_conn.send(i)
+                        low_conn.send(b'\r\n')
+                    low_conn.send(b'0\r\n\r\n')
+
+                    # Receive the response from the server
+                    try:
+                        # For Python 2.7, use buffering of HTTP responses
+                        r = low_conn.getresponse(buffering=True)
+                    except TypeError:
+                        # For compatibility with Python 3.3+
+                        r = low_conn.getresponse()
+
+                    resp = HTTPResponse.from_httplib(
+                        r,
+                        pool=conn,
+                        connection=low_conn,
+                        preload_content=False,
+                        decode_content=False
+                    )
+                except:
+                    # If we hit any problems here, clean up the connection.
+                    # Then, reraise so that we can handle the actual exception.
+                    low_conn.close()
+                    raise
 
         except (ProtocolError, socket.error) as err:
             raise ConnectionError(err, request=request)