Used a Python 3 compatible StringIO in test_utils

# -*- coding: utf-8 -*-

from __future__ import absolute_import, unicode_literals

from StringIO import StringIO

import warnings

from django.db import connection

    def test_normalizer(self):

        suite = make_doctest("test_utils.doctest_output")

        failures = unittest.TextTestRunner(stream=StringIO()).run(suite)

        failures = unittest.TextTestRunner(stream=six.StringIO()).run(suite)

        self.assertEqual(failures.failures, [])