bpo-40275: Use new test.support helper submodules in tests (GH-21764)

diff --git a/Lib/test/test_sundry.py b/Lib/test/test_sundry.py
index 2accad1..04e572c 100644
--- a/Lib/test/test_sundry.py
+++ b/Lib/test/test_sundry.py
@@ -3,15 +3,17 @@
 import platform
 import sys
 from test import support
+from test.support import import_helper
+from test.support import warnings_helper
 import unittest
 
 class TestUntestedModules(unittest.TestCase):
     def test_untested_modules_can_be_imported(self):
         untested = ('encodings', 'formatter')
-        with support.check_warnings(quiet=True):
+        with warnings_helper.check_warnings(quiet=True):
             for name in untested:
                 try:
-                    support.import_module('test.test_{}'.format(name))
+                    import_helper.import_module('test.test_{}'.format(name))
                 except unittest.SkipTest:
                     importlib.import_module(name)
                 else: