docs: def ensure_schema(client, table_name):
          """
          Create the table/columnfamily if it doesn't already exist.
  
          :param client: A Cassandra CQL client
          :type client: silverberg.client.CQLClient
  
          :param lock_table: A table/columnfamily table name for holding locks.
          :type lock_table: str
          """
          query = ''.join([
              'CREATE TABLE {cf} ',
              '("lockId" ascii, "claimId" timeuuid, PRIMARY KEY("lockId", "claimId"));'])
  
          def errback(failure):
              failure.trap(InvalidRequestException)
  
          return client.execute(query.format(cf=table_name),
                                {}, ConsistencyLevel.QUORUM).addErrback(errback)