Given the consensus hash, find the block number (or None)

def rpc_get_block_from_consensus( self, consensus_hash, **con_info ):
        """
        Given the consensus hash, find the block number (or None)
        """
        if not check_string(consensus_hash, min_length=LENGTHS['consensus_hash']*2, max_length=LENGTHS['consensus_hash']*2, pattern=OP_CONSENSUS_HASH_PATTERN):
            return {'error': 'Not a valid consensus hash', 'http_status': 400}

        db = get_db_state(self.working_dir)
        block_id = db.get_block_from_consensus( consensus_hash )
        db.close()
        return self.success_response( {'block_id': block_id} )