Use unittest.main() in 3.3 and greater

Lib/test/test_dictcomps.py

@@ -84,8 +84,5 @@ class DictComprehensionTest(unittest.TestCase):
                     "exec")
 
 
-def test_main():
-    support.run_unittest(__name__)
-
 if __name__ == "__main__":
-    test_main()
+    unittest.main()