docs: def ready(self):
          """
          Assumes postgres now talks to pg_ctl, but might not yet be listening
          or connections from psql.  Test that psql is able to connect, as
          it occasionally takes 5-10 seconds for postgresql to start listening.
          """
          cmd = self._psql_cmd()
          for i in range(50, -1, -1):
              res = subprocess.call(
                  cmd, stdin=DEV_NULL, stdout=DEV_NULL,
                  stderr=DEV_NULL)
              if res == 0:
                  break
              time.sleep(0.2)
          return i != 0