'An exception in listdir should raise a DistutilsFileError'

def test_copy_tree_exception_in_listdir(self):

    with patch('os.listdir', side_effect=OSError()):
        with self.assertRaises(errors.DistutilsFileError):
            src = self.tempdirs[(-1)]
            dir_util.copy_tree(src, None)
