Issue #25805: Skip a test for test_pkgutil when __name__ == __main__.

Thanks to SilentGhost for the patch.
diff --git a/Lib/test/test_pkgutil.py b/Lib/test/test_pkgutil.py
index a820587..ae2aa1b 100644
--- a/Lib/test/test_pkgutil.py
+++ b/Lib/test/test_pkgutil.py
@@ -413,6 +413,7 @@
             self.assertIsNotNone(pkgutil.get_loader("test.support"))
             self.assertEqual(len(w.warnings), 0)
 
+    @unittest.skipIf(__name__ == '__main__', 'not compatible with __main__')
     def test_get_loader_handles_missing_loader_attribute(self):
         global __loader__
         this_loader = __loader__