old_contents: # Skipping test_parser and test_all_fixers
  # because of running
  from lib2to3.tests import test_fixers, test_pytree, test_util
  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):
          tests.addTests(loader.loadTestsFromModule(m))
      return tests
  
  def test_main():
      run_unittest(suite())
  
  
  if __name__ == '__main__':
      test_main()
  
new_contents: # Skipping test_parser and test_all_fixers
  # because of running
  from lib2to3.tests import test_fixers, test_pytree, test_util
  import unittest
  from test.test_support import run_unittest, requires
  
  # Don't run lib2to3 tests by default since they take too long
  if __name__ != '__main__':
      requires('lib2to3')
  
  def suite():
      tests = unittest.TestSuite()
      loader = unittest.TestLoader()
      for m in (test_fixers,test_pytree,test_util):
          tests.addTests(loader.loadTestsFromModule(m))
      return tests
  
  def test_main():
      run_unittest(suite())
  
  
  if __name__ == '__main__':
      test_main()
  
subject: Disable lib2to3 by default, unless run explicitly.