provides common functionality for get_acl() and get_def_acl()

def get_acl_helper(self, key_name, headers, query_args):
        """provides common functionality for get_acl() and get_def_acl()"""
        response = self.connection.make_request('GET', self.name, key_name,
                                                query_args=query_args, 
                                                headers=headers)
        body = response.read()
        if response.status == 200:
            acl = ACL(self)
            h = handler.XmlHandler(acl, self)
            xml.sax.parseString(body, h)
            return acl
        else:
            raise self.connection.provider.storage_response_error(
                response.status, response.reason, body)