use assert[Not]IsInstance where appropriate
diff --git a/Lib/test/test_userdict.py b/Lib/test/test_userdict.py
index 3491f29..4821498 100644
--- a/Lib/test/test_userdict.py
+++ b/Lib/test/test_userdict.py
@@ -39,8 +39,8 @@
         self.assertEqual(UserDict.UserDict.fromkeys('one two'.split(), 1), d5)
         self.assertEqual(UserDict.UserDict().fromkeys('one two'.split(), 1), d5)
         self.assertTrue(u1.fromkeys('one two'.split()) is not u1)
-        self.assertTrue(isinstance(u1.fromkeys('one two'.split()), UserDict.UserDict))
-        self.assertTrue(isinstance(u2.fromkeys('one two'.split()), UserDict.IterableUserDict))
+        self.assertIsInstance(u1.fromkeys('one two'.split()), UserDict.UserDict)
+        self.assertIsInstance(u2.fromkeys('one two'.split()), UserDict.IterableUserDict)
 
         # Test __repr__
         self.assertEqual(str(u0), str(d0))