Expose socket.socketpair to Python 3.5 and below on windows. It was added in...

Expose socket.socketpair to Python 3.5 and below on windows. It was added in 3.5, and is an extension for earlier versions.

CHANGES.rst

@@ -8,9 +8,12 @@
 ==================
 
 - CI services now test on 3.6.0.
-- Windows: Provide ``socket.socketpair`` on 3.6.
+- Windows: Provide ``socket.socketpair`` for all Python 3 versions.
+  This was added to Python 3.5, but tests were only added in 3.6.
+  (For versions older than 3.4 this is a gevent extension.) Previously
+  this was not supported on any Python 3 version.
 - Windows: List ``subprocess.STARTUPINFO`` in ``subprocess.__all__``
-  on 3.6.
+  for 3.6 compatibility.
 - The ``_DummyThread`` objects created by calling
   :func:`threading.current_thread` from inside a raw
   :class:`greenlet.greenlet` now clean up after themselves when the

src/gevent/_socket3.py

@@ -644,6 +644,10 @@ if hasattr(_socket, "socketpair"):
         socketpair() function.
         The arguments are the same as for socket() except the default family is
         AF_UNIX if defined on the platform; otherwise, the default is AF_INET.
+
+        .. versionchanged:: 1.2
+           All Python 3 versions on Windows supply this function (natively
+           supplied by Python 3.5 and above).
         """
         if family is None:
             try:
@@ -655,13 +659,13 @@ if hasattr(_socket, "socketpair"):
         b = socket(family, type, proto, b.detach())
         return a, b
 
-elif sys.version_info[:2] >= (3, 6):
+else:
     # Origin: https://gist.github.com/4325783, by Geert Jansen.  Public domain.
 
-    # gevent: taken from 3.6 release. Expected to be used only on Win/3.6
-    # gevent: for testing on < 3.5, pass the default value of 128 to lsock.listen()
+    # gevent: taken from 3.6 release. Expected to be used only on Win. Added to Win/3.5
+    # gevent: for < 3.5, pass the default value of 128 to lsock.listen()
     # (3.5+ uses this as a default and the original code passed no value)
-    # gevent: TODO: Expose this for all versions?
+
     _LOCALHOST = '127.0.0.1'
     _LOCALHOST_V6 = '::1'
 
@@ -702,12 +706,15 @@ elif sys.version_info[:2] >= (3, 6):
             lsock.close()
         return (ssock, csock)
 
-elif 'socketpair' in __implements__:
-    # Win32: not available prior to 3.6
-    # Multiple imports can cause this to be missing if _socketcommon
-    # was successfully imported, leading to subsequent imports to cause
-    # ValueError
-    __implements__.remove('socketpair')
+    if sys.version_info[:2] < (3, 5):
+        # Not provided natively
+        if 'socketpair' in __implements__:
+            # Multiple imports can cause this to be missing if _socketcommon
+            # was successfully imported, leading to subsequent imports to cause
+            # ValueError
+            __implements__.remove('socketpair')
+        if 'socketpair' not in __extensions__:
+            __extensions__.append('socketpair')
 
 
 # PyPy needs drop and reuse