bpo-40275: Adding threading_helper submodule in test.support (GH-20263)

diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 33b3459..2f93eaa 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -1,5 +1,3 @@
-from test import support
-from test.support.script_helper import assert_python_ok, assert_python_failure
 import builtins
 import codecs
 import gc
@@ -11,6 +9,9 @@
 import sys
 import sysconfig
 import test.support
+from test import support
+from test.support.script_helper import assert_python_ok, assert_python_failure
+from test.support import threading_helper
 import textwrap
 import unittest
 import warnings
@@ -365,7 +366,7 @@
         )
 
     # sys._current_frames() is a CPython-only gimmick.
-    @test.support.reap_threads
+    @threading_helper.reap_threads
     def test_current_frames(self):
         import threading
         import traceback