Allow absent fromfd(), for Windows.

Lib/test/test_socket.py

@@ -323,6 +323,8 @@ class BasicTCPTest(SocketConnectedTest):
 
     def testFromFd(self):
         """Testing fromfd()."""
+        if not hasattr(socket, fromfd):
+            return # On Windows, this doesn't exist
         fd = self.cli_conn.fileno()
         sock = socket.fromfd(fd, socket.AF_INET, socket.SOCK_STREAM)
         msg = sock.recv(1024)