Fixed a test failure due to Django 1.8 TestCase change.

Django 1.8 no longer resets the URLconf before each test class.
django/django@d89f56d#diff-5d7d8ead1a907fe91ffc121f830f2a49L229

docs/tests.py

@@ -1,4 +1,5 @@
 from django.contrib.sites.models import Site
+from django.core.urlresolvers import set_urlconf
 from django.test import TestCase
 
 
@@ -9,6 +10,12 @@ def setUp(self):
         # We need to create an extra Site because docs have SITE_ID=2
         Site.objects.create(name='Django test', domain="example.com")
 
+    @classmethod
+    def tearDownClass(cls):
+        # cleanup URLconfs changed by django-hosts
+        set_urlconf(None)
+        super(SearchFormTestCase, cls).tearDownClass()
+
     def test_empty_get(self):
         response = self.client.get('/en/dev/search/',
                                    HTTP_HOST='docs.djangoproject.dev:8000')