Adapt to use the test_main() approach.
diff --git a/Lib/test/test_htmlparser.py b/Lib/test/test_htmlparser.py
index 8661066..85e60e6 100755
--- a/Lib/test/test_htmlparser.py
+++ b/Lib/test/test_htmlparser.py
@@ -280,4 +280,9 @@
             ])
 
 
-test_support.run_unittest(HTMLParserTestCase)
+def test_main():
+    test_support.run_unittest(HTMLParserTestCase)
+
+
+if __name__ == "__main__":
+    test_main()