Fix issues in the requests wrapper with urllib3 1.21.* and 1.25.*

For older `urllib3` versions an attribute we assumed to be present was not,
causing a crash.

For the latest version inheriting our patched `HTTPSConnectionPool` class from
the wrong base class `urllib3.HTTPConnectionPool` (rather than
`urllib3.HTTPSConnectionPool`) caused HTTPS validation to mysteriously fail,
as the system CA store wasn't loaded anymore.

Author: ntninja

ipfshttpclient/http.py

@@ -10,6 +10,7 @@
 import functools
 import tarfile
 from six.moves import http_client
+import os
 import socket
 try:  #PY3
 	import urllib.parse
@@ -23,7 +24,12 @@ class urllib:
 
 from . import encoding
 from . import exceptions
-from . import requests_wrapper as requests
+PATCH_REQUESTS = (os.environ.get("PY_IPFS_HTTP_CLIENT_PATCH_REQUESTS", "yes").lower()
+                  not in ("false", "no"))
+if PATCH_REQUESTS:
+	from . import requests_wrapper as requests
+else:  # pragma: no cover (always enabled in production)
+	import requests
 
 
 def pass_defaults(func):
@@ -210,9 +216,9 @@ def __init__(self, addr, base, **defaults):
 			query    = "",
 			fragment = ""
 		).geturl()
-		self._kwargs = {
-			"family": family
-		}
+		self._kwargs = {}
+		if PATCH_REQUESTS:  # pragma: no branch (always enabled in production)
+			self._kwargs["family"] = family
 
 		self.defaults = defaults
 		self._session = None

ipfshttpclient/requests_wrapper.py

@@ -97,8 +97,9 @@ def _new_conn(self):
 			extra_kw['socket_options'] = self.socket_options
 
 		try:
+			dns_host = getattr(self, "_dns_host", self.host)
 			conn = create_connection(
-				(self._dns_host, self.port), self.timeout, **extra_kw)
+				(dns_host, self.port), self.timeout, **extra_kw)
 		except socket.timeout:
 			raise urllib3.exceptions.ConnectTimeoutError(
 				self, "Connection to %s timed out. (connect timeout=%s)" %
@@ -128,7 +129,7 @@ class HTTPConnectionPool(urllib3.HTTPConnectionPool):
 	ConnectionCls = HTTPConnection
 
 
-class HTTPSConnectionPool(urllib3.HTTPConnectionPool):
+class HTTPSConnectionPool(urllib3.HTTPSConnectionPool):
 	ConnectionCls = HTTPSConnection
 
 
@@ -158,11 +159,14 @@ def _new_pool(self, scheme, host, port, request_context=None):
 		if request_context is None:
 			request_context = self.connection_pool_kw.copy()
 
+		for key in ('host', 'port'):
+			request_context.pop(key, None)
+		
 		if scheme == "http" or scheme.startswith("http+"):
 			for kw in urllib3.poolmanager.SSL_KEYWORDS:
 				request_context.pop(kw, None)
 
-		return pool_cls(**request_context)
+		return pool_cls(host, port, **request_context)
 
 	def connection_from_pool_key(self, pool_key, request_context=None):
 		# Copied from `urllib3` so that we continue to ensure that this will