tl;dr: wait a bit to update gnome3 or you should build from source If you're like me and follow -current and happened to do a `pkg_update -Uu` blindly in the last few days, you may have upgraded gnome3 to the latest (from 3.26).
Currently it has potential to bork GDM and you won't get a login screen (I got a black screen with cursor). In my case, it seems the gnome-weather app/service was crashing at start-up...and for some gnome-ish reason it took down the whole gnome-shell. (Yes, startx with a blank .xinitrc work[s/ed] fine loading fvwm, so it wasn't xorg issues.) The good news is (for at least on my machine) some issues have already been identified and fixed by aja@ and jasperla@ (and reported upstream). Thanks to you two! -Dave
