Ignore broken barrier errors when waiting on the barrier in the main process

Author: duaneg

Lib/test/test_concurrent_futures/executor.py

@@ -243,7 +243,10 @@ def test_shutdown_notifies_cancelled_futures(self):
               for index in range(count)]
 
         self.executor.shutdown(wait=False, cancel_futures=True)
-        barrier.wait()
+        try:
+            barrier.wait()
+        except threading.BrokenBarrierError:
+            pass
 
         for future in fs:
             self.assertRaises((FalseyBoolException, futures.CancelledError),