'The only valid values for \'action\' on XenServer are \'reboot\' or
\'shutdown\', even though the API also accepts \'startup\'. As this is
not technically possible on XenServer, since the host is the same
physical machine as the hypervisor, if this is requested, we need to
raise an exception.'

def host_power_action(self, action):

    if (action in ('reboot', 'shutdown')):
        return self._host.host_power_action(action)
    else:
        msg = _('Host    startup    on    XenServer    is    not    supported.')
        raise NotImplementedError(msg)
