Silence fork-in-thread warnings, incidentally fixing a mysterious and prima

facie unrelated unit test failure/hang.

Author: duaneg

Lib/test/test_concurrent_futures/executor.py

@@ -248,6 +248,7 @@ def test_swallows_falsey_exceptions(self):
         with self.assertRaisesRegex(FalseyLenException, msg):
             self.executor.submit(raiser, FalseyLenException, msg).result()
 
+    @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
     def test_shutdown_notifies_cancelled_futures(self):
 
         # TODO: remove when gh-109934 is fixed