There has been work to solve this by registering the session, compositor, and screen locker each with the session manager.
If the screen locker (which now can use any toolkit) crashes, the session manager can try to restart it. If it fails again, it just displays "your unlocker has crashed. To unlock this session, open a tty, login, and type `loginctl session-unlock`"
This solves all the issues, but he (and many others) have been fighting against systemd for a while (which fixes this, and so many other issues, which no competing project ever handled)
DON'T OPEN THAT LINK
https://news.ycombinator.com/item?id=11135200
>sirsar: JWZ used to detect the hacker news referrer and redirect all links that originated on hacker news to goatse. Now it's only slightly less graphic
Basically HN is him when he worked for Netscape and he doesn't like the reminder...