bpo-40275: Use new test.support helper submodules in tests (GH-21412)

diff --git a/Lib/test/test_contextlib.py b/Lib/test/test_contextlib.py
index 024f912..50943c1 100644
--- a/Lib/test/test_contextlib.py
+++ b/Lib/test/test_contextlib.py
@@ -7,6 +7,7 @@
 import unittest
 from contextlib import *  # Tests __all__
 from test import support
+from test.support import os_helper
 import weakref
 
 
@@ -327,7 +328,7 @@
                     1 / 0
             self.assertTrue(f.closed)
         finally:
-            support.unlink(tfn)
+            os_helper.unlink(tfn)
 
 class LockContextTestCase(unittest.TestCase):