Replace catch_warnings with check_warnings when it makes sense. Use assertRaises context manager to simplify some tests.

Lib/test/test_argparse.py

@@ -7,7 +7,6 @@ import sys
 import textwrap
 import tempfile
 import unittest
-import warnings
 import argparse
 
 from StringIO import StringIO
@@ -4160,21 +4159,12 @@ class TestImportStar(TestCase):
             self.assertTrue(hasattr(argparse, name))
 
 def test_main():
-    with warnings.catch_warnings():
-        # silence warnings about version argument - these are expected
-        warnings.filterwarnings(
-            action='ignore',
-            message='The "version" argument to ArgumentParser is deprecated.',
-            category=DeprecationWarning)
-        warnings.filterwarnings(
-            action='ignore',
-            message='The format_version method is deprecated',
-            category=DeprecationWarning)
-        warnings.filterwarnings(
-            action='ignore',
-            message='The print_version method is deprecated',
-            category=DeprecationWarning)
-
+    # silence warnings about version argument - these are expected
+    with test_support.check_warnings(
+            ('The "version" argument to ArgumentParser is deprecated.',
+             DeprecationWarning),
+            ('The (format|print)_version method is deprecated',
+             DeprecationWarning)):
         test_support.run_unittest(__name__)
     # Remove global references to avoid looking like we have refleaks.
     RFile.seen = {}