use assert[Not]IsInstance where appropriate
diff --git a/Lib/test/test_opcodes.py b/Lib/test/test_opcodes.py
index c03ca1d..77090da 100644
--- a/Lib/test/test_opcodes.py
+++ b/Lib/test/test_opcodes.py
@@ -64,7 +64,7 @@
 
         try:  raise DClass, a
         except DClass, v:
-            self.assertTrue(isinstance(v, DClass))
+            self.assertIsInstance(v, DClass)
         else:
             self.fail("no exception")