gh-128364: Fix flaky test_timeout test

Author: colesbury

Lib/test/test_concurrent_futures/test_wait.py

@@ -114,9 +114,9 @@ def test_all_completed(self):
 
     def test_timeout(self):
         short_timeout = 0.050
-        long_timeout = short_timeout * 10
+        event = threading.Event()
 
-        future = self.executor.submit(time.sleep, long_timeout)
+        future = self.executor.submit(event.wait)
 
         finished, pending = futures.wait(
                 [CANCELLED_AND_NOTIFIED_FUTURE,
@@ -126,6 +126,9 @@ def test_timeout(self):
                 timeout=short_timeout,
                 return_when=futures.ALL_COMPLETED)
 
+        event.set()
+        futures.wait([future], return_when=futures.ALL_COMPLETED)
+
         self.assertEqual(set([CANCELLED_AND_NOTIFIED_FUTURE,
                               EXCEPTION_FUTURE,
                               SUCCESSFUL_FUTURE]),