QTdragon HD with MDI issue

/bin/sh: 1: gnome-session-quit: not found
Shutting down and cleaning up LinuxCNC...
Running HAL shutdown script

    def SHUT_SYSTEM_DOWN_PROMPT(self):
        import subprocess
        try:
            try:
                subprocess.call('gnome-session-quit --power-off', shell=True)
            except:
                try:
                    subprocess.call('xfce4-session-logout', shell=True)
                except:
                    try:
                        subprocess.call('systemctl poweroff', shell=True)
                    except:
                        raise
        except Exception as e:
            LOG.warning("Couldn't shut system down: {}".format(e))