Fixed #21518 -- Made override_settings(ROOT_URLCONF) clear the resolver cache.

        # stacklevel=5 shows the line containing the override_settings call.

        warnings.warn("Overriding setting %s can lead to unexpected behaviour."

                      % kwargs['setting'], stacklevel=5)

@receiver(setting_changed)

def root_urlconf_changed(**kwargs):

    if kwargs['setting'] == 'ROOT_URLCONF':

        from django.core.urlresolvers import clear_url_caches

        clear_url_caches()

import unittest

from django.conf.urls import patterns, url

from django.core.urlresolvers import reverse

from django.db import connection

from django.forms import EmailField, IntegerField

from django.http import HttpResponse

from django.template.loader import render_to_string

from django.test import SimpleTestCase, TestCase, skipIfDBFeature, skipUnlessDBFeature

from django.test.html import HTMLParseError, parse_html

from django.test.utils import CaptureQueriesContext, IgnoreAllDeprecationWarningsMixin

from django.test.utils import (CaptureQueriesContext,

    IgnoreAllDeprecationWarningsMixin, override_settings)

from django.utils import six

from .models import Person

        suite = make_doctest("test_utils.doctest_output")

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

        self.assertEqual(failures.failures, [])

# for OverrideSettingsTests

def fake_view(request):

    pass

class FirstUrls:

    urlpatterns = patterns('', url(r'first/$', fake_view, name='first'))

class SecondUrls:

    urlpatterns = patterns('', url(r'second/$', fake_view, name='second'))

class OverrideSettingsTests(TestCase):

    """

    #21518 -- If neither override_settings nor a settings_changed receiver

    clears the URL cache between tests, then one of these two test methods will

    fail.

    """

    @override_settings(ROOT_URLCONF=FirstUrls)

    def test_first(self):

        reverse('first')

    @override_settings(ROOT_URLCONF=SecondUrls)

    def test_second(self):

        reverse('second')