Fixed #14508 - test suite silences warnings.

Utility functions get_warnings_state and save_warnings_state have been added
to django.test.utils, and methods to django.test.TestCase for convenience.

The implementation is based on the catch_warnings context manager from
Python 2.6.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14526 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/test/testcases.py

@@ -11,6 +11,7 @@ from django.db import transaction, connection, connections, DEFAULT_DB_ALIAS
 from django.http import QueryDict
 from django.test import _doctest as doctest
 from django.test.client import Client
+from django.test.utils import get_warnings_state, restore_warnings_state
 from django.utils import simplejson, unittest as ut2
 from django.utils.encoding import smart_str
 from django.utils.functional import wraps
@@ -328,6 +329,19 @@ class TransactionTestCase(ut2.TestCase):
             settings.ROOT_URLCONF = self._old_root_urlconf
             clear_url_caches()
 
+    def save_warnings_state(self):
+        """
+        Saves the state of the warnings module
+        """
+        self._warnings_state = get_warnings_state()
+
+    def restore_warnings_state(self):
+        """
+        Restores the sate of the warnings module to the state
+        saved by save_warnings_state()
+        """
+        restore_warnings_state(self._warnings_state)
+
     def assertRedirects(self, response, expected_url, status_code=302,
                         target_status_code=200, host=None, msg_prefix=''):
         """Asserts that a response redirected to a specific URL, and that the