gh-88110: clear concurrent.futures.thread._threads_queues after fork to avoid joining parent process' threads

Lib/test/test_concurrent_futures/test_thread_pool.py

@@ -4,6 +4,7 @@
 import multiprocessing.util
 import os
 import threading
+import warnings
 import unittest
 from concurrent import futures
 from test import support
@@ -67,14 +68,16 @@ def submit(pool):
                     workers.submit(tuple)
 
     @support.requires_fork()
-    @unittest.skipUnless(hasattr(os, 'register_at_fork'), 'need os.register_at_fork')
-    @support.requires_resource('cpu')
+    @unittest.skipUnless(hasattr(os, "register_at_fork"), "need os.register_at_fork")
+    @support.requires_resource("cpu")
     def test_process_fork_from_a_threadpool(self):
         # bpo-43944: clear concurrent.futures.thread._threads_queues after fork,
         # otherwise child process will try to join parent thread
         def fork_process_and_return_exitcode():
-            p = mp.get_context('fork').Process(target=lambda: 1)
-            p.start()
+            # Ignore the warning about fork with threads.
+            with warnings.catch_warnings(category=DeprecationWarning, action="ignore"):
+                p = mp.get_context("fork").Process(target=lambda: 1)
+                p.start()
             p.join()
             return p.exitcode