def _validate_power_state(self, node_uuid, power_state):
        # Validate that power state is set within timeout
        if power_state == 'rebooting':
            power_state = 'power on'
        start = timeutils.utcnow()
        while timeutils.delta_seconds(
                start, timeutils.utcnow()) < self.power_timeout:
            resp, node = self.client.show_node(node_uuid)
            self.assertEqual(200, resp.status)
            if node['power_state'] == power_state:
                 return False
        message = ('Failed to set power state within '
                   'the required time: %s sec.' % self.power_timeout)
        raise exceptions.TimeoutException(message)