Bug#804893: Fwd: Cannot run gnome without gdm3 installed.

[Net Kgk]

Package: gnome-shell
Version: 3.18.1-1

Trying to intall crap-free gnome environment (i.e. no python, no
polkit, no systemd). As gdm3 heavily depends on the crap #1 (python),
this is first candidate to replace, but `gnome-shell` refuse to start
if `gdm3` package isn't installed:
```
(gnome-shell:2945): GLib-GIO-ERROR **: Settings schema
'org.gnome.login-screen' is not installed
```