Fixed #15026 -- Added cleanup to the invalid key session tests; when using Memcached as a cache backend, the cache-backed session backends would fail on the second run due to leftover cache artefacts. Thanks to jsdalton for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15235 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/sessions/tests.py

@@ -160,11 +160,16 @@ class SessionTestsMixin(object):
     def test_invalid_key(self):
         # Submitting an invalid session key (either by guessing, or if the db has
         # removed the key) results in a new key being generated.
+        try:
             session = self.backend('1')
             session.save()
             self.assertNotEqual(session.session_key, '1')
             self.assertEqual(session.get('cat'), None)
             session.delete()
+        finally:
+            # Some backends leave a stale cache entry for the invalid
+            # session key; make sure that entry is manually deleted
+            session.delete('1')
 
     # Custom session expiry
     def test_default_expiry(self):