Comment 3 for bug 623717

Yes, that's just a warning that we couldn't contact the logind service (as provided by systemd). It should probably be just be a debugging message as we fallback to using ConsoleKit instead. I think if ConsoleKit is also not available we fall back to nothing (haven't tested it)

In short, you probably don't need to do much with logind/ConsoleKit on Slackware, LightDM should just continue to work with slightly less features.