Invoke test_urllibnet tests using unittest.main function

Lib/test/test_urllibnet.py

@@ -10,6 +10,8 @@ import email.message
 import time
 
 
+support.requires('network')
+
 class URLTimeoutTest(unittest.TestCase):
     # XXX this test doesn't seem to test anything useful.
 
@@ -206,11 +208,5 @@ class urlretrieveNetworkTests(unittest.TestCase):
                                 " >= total size in %s" % records_repr)
 
 
-def test_main():
-    support.requires('network')
-    support.run_unittest(URLTimeoutTest,
-                         urlopenNetworkTests,
-                         urlretrieveNetworkTests)
-
 if __name__ == "__main__":
-    test_main()
+    unittest.main()