'Try to connect to the given dbus services. If successful it will
return a callable dbus proxy and those arguments.'

def _prepair(self):

    try:
        sessionbus = dbus.SessionBus()
        systembus = dbus.SystemBus()
    except:
        return (None, None)
    for dbus_props in self.DBUS_SHUTDOWN.values():
        try:
            if (dbus_props['bus'] == SESSION_BUS):
                bus = sessionbus
            else:
                bus = systembus
            interface = bus.get_object(dbus_props['service'], dbus_props['objectPath'])
            proxy = interface.get_dbus_method(dbus_props['method'], dbus_props['interface'])
            return (proxy, dbus_props['arguments'])
        except dbus.exceptions.DBusException:
            continue
    return (None, None)
