Skip test that fails randomly on PyPy.

Fix #1314.

Author: aaugustin

tests/sync/test_connection.py

@@ -1,5 +1,6 @@
 import contextlib
 import logging
+import platform
 import socket
 import sys
 import threading
@@ -465,6 +466,10 @@ def test_close_idempotency(self):
         self.connection.close()
         self.assertNoFrameSent()
 
+    @unittest.skipIf(
+        platform.python_implementation() == "PyPy",
+        "this test fails randomly due to a bug in PyPy",  # see #1314 for details
+    )
     def test_close_idempotency_race_condition(self):
         """close waits if the connection is already closing."""