bpo-40275: Use new test.support helper submodules in tests (GH-21448)

Lib/test/test_argparse.py

@@ -13,6 +13,7 @@ import argparse
 from io import StringIO
 
 from test import support
+from test.support import os_helper
 from unittest import mock
 class StdIOBuffer(StringIO):
     pass
@@ -23,7 +24,7 @@ class TestCase(unittest.TestCase):
         # The tests assume that line wrapping occurs at 80 columns, but this
         # behaviour can be overridden by setting the COLUMNS environment
         # variable.  To ensure that this width is used, set COLUMNS to 80.
-        env = support.EnvironmentVarGuard()
+        env = os_helper.EnvironmentVarGuard()
         env['COLUMNS'] = '80'
         self.addCleanup(env.__exit__)
 
@@ -3244,7 +3245,7 @@ class TestShortColumns(HelpTestCase):
     but we don't want any exceptions thrown in such cases. Only ugly representation.
     '''
     def setUp(self):
-        env = support.EnvironmentVarGuard()
+        env = os_helper.EnvironmentVarGuard()
         env.set("COLUMNS", '15')
         self.addCleanup(env.__exit__)