Make the test more robust

Author: encukou

Lib/test/test_threading.py

@@ -445,9 +445,14 @@ def catch_exception():
         self.assertEqual(result, 1)
 
         for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
-            signal.pthread_kill(thread.ident, signal.SIGUSR1)
             if not thread.is_alive():
                 break
+            try:
+                signal.pthread_kill(thread.ident, signal.SIGUSR1)
+            except OSError:
+                # The thread might have terminated between the is_alive check
+                # and the pthread_kill
+                break
 
         thread.join()
         signal.signal(signal.SIGUSR1, signal.SIG_DFL)