def _lookup_constraint_references(self, table_name, cname):
        """
        Provided an existing table and constraint, returns tuple of (foreign
        table, column)
        """
        db_name = self._get_setting('NAME')
        try:
            return self._constraint_references[db_name][(table_name, cname)]
        except __HOLE__:
            return None
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/South-1.0.2/south/db/mysql.py/DatabaseOperations._lookup_constraint_references