Fix unstable test

Author: fantix

tests/test_tcp.py

@@ -2478,8 +2478,13 @@ def server(sock):
 
             # send close_notify but don't wait for response
             sock.setblocking(0)
-            with self.assertRaises(ssl.SSLWantReadError):
-                sock.unwrap()
+            try:
+                with self.assertRaises(ssl.SSLWantReadError):
+                    sock.unwrap()
+            except OSError as ex:
+                # sometimes the network is faster
+                if ex.errno != 0:
+                    raise
             sock.setblocking(1)
 
             # should receive all data