Clean up warnings filter use in test_bytes.

Lib/test/test_bytes.py

@@ -27,12 +27,6 @@ class Indexable:
 
 class BaseBytesTest(unittest.TestCase):
 
-    def setUp(self):
-        self.warning_filters = warnings.filters[:]
-
-    def tearDown(self):
-        warnings.filters = self.warning_filters
-
     def test_basics(self):
         b = self.type2test()
         self.assertEqual(type(b), self.type2test)
@@ -127,13 +121,17 @@ class BaseBytesTest(unittest.TestCase):
         self.assertFalse(b3 <= b2)
 
     def test_compare_to_str(self):
+        with test.support.check_warnings():
             warnings.simplefilter('ignore', BytesWarning)
             # Byte comparisons with unicode should always fail!
-        # Test this for all expected byte orders and Unicode character sizes
+            # Test this for all expected byte orders and Unicode character
+            # sizes.
             self.assertEqual(self.type2test(b"\0a\0b\0c") == "abc", False)
-        self.assertEqual(self.type2test(b"\0\0\0a\0\0\0b\0\0\0c") == "abc", False)
+            self.assertEqual(self.type2test(b"\0\0\0a\0\0\0b\0\0\0c") == "abc",
+                                False)
             self.assertEqual(self.type2test(b"a\0b\0c\0") == "abc", False)
-        self.assertEqual(self.type2test(b"a\0\0\0b\0\0\0c\0\0\0") == "abc", False)
+            self.assertEqual(self.type2test(b"a\0\0\0b\0\0\0c\0\0\0") == "abc",
+                                False)
             self.assertEqual(self.type2test() == str(), False)
             self.assertEqual(self.type2test() != str(), True)
 
@@ -829,13 +827,8 @@ class AssortedBytesTest(unittest.TestCase):
     # Test various combinations of bytes and bytearray
     #
 
-    def setUp(self):
-        self.warning_filters = warnings.filters[:]
-
-    def tearDown(self):
-        warnings.filters = self.warning_filters
-
     def test_repr_str(self):
+        with test.support.check_warnings():
             warnings.simplefilter('ignore', BytesWarning)
             for f in str, repr:
                 self.assertEqual(f(bytearray()), "bytearray(b'')")
@@ -888,6 +881,7 @@ class AssortedBytesTest(unittest.TestCase):
         self.assertEqual(b, bytearray(sample))
 
     def test_to_str(self):
+        with test.support.check_warnings():
             warnings.simplefilter('ignore', BytesWarning)
             self.assertEqual(str(b''), "b''")
             self.assertEqual(str(b'x'), "b'x'")
@@ -940,11 +934,16 @@ class AssortedBytesTest(unittest.TestCase):
 
     def test_compare(self):
         if sys.flags.bytes_warning:
+            with test.support.check_warnings():
                 warnings.simplefilter('error', BytesWarning)
-            self.assertRaises(BytesWarning, operator.eq, b'', '')
-            self.assertRaises(BytesWarning, operator.ne, b'', '')
-            self.assertRaises(BytesWarning, operator.eq, bytearray(b''), '')
-            self.assertRaises(BytesWarning, operator.ne, bytearray(b''), '')
+                with self.assertRaises(BytesWarning):
+                    b'' == ''
+                with self.assertRaises(BytesWarning):
+                    b'' != ''
+                with self.assertRaises(BytesWarning):
+                    bytearray(b'') == ''
+                with self.assertRaises(BytesWarning):
+                    bytearray(b'') != ''
         else:
             # self.skipTest("BytesWarning is needed for this test: use -bb option")
             pass