bpo-45046: Support context managers in unittest (GH-28045)

Add methods enterContext() and enterClassContext() in TestCase.
Add method enterAsyncContext() in IsolatedAsyncioTestCase.
Add function enterModuleContext().

1 files changed, 2 insertions, 4 deletions

diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
index 8509deb93f1..273db45c00f 100644
--- a/Lib/test/test_argparse.py
+++ b/Lib/test/test_argparse.py
@@ -41,9 +41,8 @@ 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 = os_helper.EnvironmentVarGuard()
+        env = self.enterContext(os_helper.EnvironmentVarGuard())
         env['COLUMNS'] = '80'
-        self.addCleanup(env.__exit__)
 
 
 class TempDirMixin(object):
@@ -3428,9 +3427,8 @@ class TestShortColumns(HelpTestCase):
     but we don't want any exceptions thrown in such cases. Only ugly representation.
     '''
     def setUp(self):
-        env = os_helper.EnvironmentVarGuard()
+        env = self.enterContext(os_helper.EnvironmentVarGuard())
         env.set("COLUMNS", '15')
-        self.addCleanup(env.__exit__)
 
     parser_signature            = TestHelpBiggerOptionals.parser_signature
     argument_signatures         = TestHelpBiggerOptionals.argument_signatures