asyncio: use directly socket.socketpair() (#4597)

Since Python 3.5, socket.socketpair() is also available on Windows,
and so can be used directly, rather than using
asyncio.windows_utils.socketpair().

Lib/test/test_asyncio/test_proactor_events.py

@@ -444,15 +444,13 @@ class BaseProactorEventLoopTests(test_utils.TestCase):
 
         self.ssock, self.csock = mock.Mock(), mock.Mock()
 
-        class EventLoop(BaseProactorEventLoop):
-            def _socketpair(s):
-                return (self.ssock, self.csock)
-
-        self.loop = EventLoop(self.proactor)
+        with mock.patch('asyncio.proactor_events.socket.socketpair',
+                        return_value=(self.ssock, self.csock)):
+            self.loop = BaseProactorEventLoop(self.proactor)
         self.set_event_loop(self.loop)
 
     @mock.patch.object(BaseProactorEventLoop, 'call_soon')
-    @mock.patch.object(BaseProactorEventLoop, '_socketpair')
+    @mock.patch('asyncio.proactor_events.socket.socketpair')
     def test_ctor(self, socketpair, call_soon):
         ssock, csock = socketpair.return_value = (
             mock.Mock(), mock.Mock())
@@ -506,14 +504,6 @@ class BaseProactorEventLoopTests(test_utils.TestCase):
         self.loop.sock_accept(self.sock)
         self.proactor.accept.assert_called_with(self.sock)
 
-    def test_socketpair(self):
-        class EventLoop(BaseProactorEventLoop):
-            # override the destructor to not log a ResourceWarning
-            def __del__(self):
-                pass
-        self.assertRaises(
-            NotImplementedError, EventLoop, self.proactor)
-
     def test_make_socket_transport(self):
         tr = self.loop._make_socket_transport(self.sock, asyncio.Protocol())
         self.assertIsInstance(tr, _ProactorSocketTransport)

Lib/test/test_asyncio/test_selector_events.py

@@ -154,9 +154,6 @@ class BaseSelectorEventLoopTests(test_utils.TestCase):
         self.loop.close()
         self.assertIsNone(self.loop._selector)
 
-    def test_socketpair(self):
-        self.assertRaises(NotImplementedError, self.loop._socketpair)
-
     def test_read_from_self_tryagain(self):
         self.loop._ssock.recv.side_effect = BlockingIOError
         self.assertIsNone(self.loop._read_from_self())

Lib/test/test_asyncio/test_windows_events.py

@@ -1,4 +1,5 @@
 import os
+import socket
 import sys
 import unittest
 from unittest import mock
@@ -36,7 +37,7 @@ class ProactorTests(test_utils.TestCase):
         self.set_event_loop(self.loop)
 
     def test_close(self):
-        a, b = self.loop._socketpair()
+        a, b = socket.socketpair()
         trans = self.loop._make_socket_transport(a, asyncio.Protocol())
         f = asyncio.ensure_future(self.loop.sock_recv(b, 100))
         trans.close()