def get_key_columns(self, cursor, table_name):
        raise NotImplementedError
Get failed repositories from failed node.
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.4/django/db/backends/__init__.py/BaseDatabaseIntrospection.get_key_columns--crossover with--dataset/ETHPy150Open openstack/fuel-web/nailgun/nailgun/rpc/receiver.py/NailgunReceiver._get_failed_repos