enable test_main.py

Lib/test/test_lib2to3.py

 # Skipping test_parser and test_all_fixers
 # because of running
 from lib2to3.tests import (test_fixers, test_pytree, test_util, test_refactor,
-                           test_parser)
+                           test_parser, test_main as test_main_)
 import unittest
 from test.test_support import run_unittest
 
 def suite():
     tests = unittest.TestSuite()
     loader = unittest.TestLoader()
-    for m in (test_fixers, test_pytree,test_util, test_refactor, test_parser):
+    for m in (test_fixers, test_pytree,test_util, test_refactor, test_parser,
+              test_main_):
         tests.addTests(loader.loadTestsFromModule(m))
     return tests