Fix for broken build 721 due to safe parameter

celery/tests/backends/test_mongodb.py

@@ -289,7 +289,7 @@ class test_MongoBackend(AppCase):
         mock_database.__getitem__.assert_called_once_with(
             MONGODB_COLLECTION)
         mock_collection.remove.assert_called_once_with(
-            {'_id': sentinel.task_id}, safe=True)
+            {'_id': sentinel.task_id})
 
     @patch('celery.backends.mongodb.MongoBackend._get_database')
     def test_cleanup(self, mock_get_database):