Fixed a flaky test.

import os

import unittest

import warnings

                self.assertEqual(settings.TEST_WARN, 'override')

            self.assertEqual(len(w), 1)

            self.assertEqual(w[0].filename, __file__)

            # File extension may by .py, .pyc, etc. Compare only basename.

            self.assertEqual(os.path.splitext(w[0].filename)[0],

                             os.path.splitext(__file__)[0])

            self.assertEqual(str(w[0].message),

                'Overriding setting TEST_WARN can lead to unexpected behaviour.')