docs: def pg_isready(self):
          """Runs pg_isready to see if PostgreSQL is accepting connections.
  
          :returns: 'ok' if PostgreSQL is up, 'reject' if starting up, 'no_resopnse' if not up."""
  
          cmd = [self._pgcommand('pg_isready'), '-p', self._local_address['port'], '-d', self._database]
  
          # Host is not set if we are connecting via default unix socket
          if 'host' in self._local_address:
              cmd.extend(['-h', self._local_address['host']])
  
          # We only need the username because pg_isready does not try to authenticate
          if 'username' in self._superuser:
              cmd.extend(['-U', self._superuser['username']])
  
          ret = subprocess.call(cmd)
          return_codes = {0: STATE_RUNNING,
                          1: STATE_REJECT,
                          2: STATE_NO_RESPONSE,
                          3: STATE_UNKNOWN}
          return return_codes.get(ret, STATE_UNKNOWN)