docs: def table_ensure(cls, rr):
          '''
          Creates the table if it doesn't exist.
          '''
          dbs = rr.db_list().run()
          if not rr.dbname in dbs:
              logging.info('creating rethinkdb database %s', repr(rr.dbname))
              rr.db_create(rr.dbname).run()
          tables = rr.table_list().run()
          if not cls.table in tables:
              logging.info(
                      'creating rethinkdb table %s in database %s',
                      repr(cls.table), repr(rr.dbname))
              cls.table_create(rr)