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

diff --git a/Lib/test/test_robotparser.py b/Lib/test/test_robotparser.py
index a3112b8..b0bed43 100644
--- a/Lib/test/test_robotparser.py
+++ b/Lib/test/test_robotparser.py
@@ -5,6 +5,7 @@
 import urllib.robotparser
 from test import support
 from test.support import socket_helper
+from test.support import threading_helper
 from http.server import BaseHTTPRequestHandler, HTTPServer
 
 
@@ -330,7 +331,7 @@
         self.t.join()
         self.server.server_close()
 
-    @support.reap_threads
+    @threading_helper.reap_threads
     def testPasswordProtectedSite(self):
         addr = self.server.server_address
         url = 'http://' + socket_helper.HOST + ':' + str(addr[1])