Issue description

For a few days (maybe 2 weeks or so), virtmanager refuses to start.

Starting from Kicker the icons shows up for a short while, then disappears.

Starting from the terminal I get this feedback:

virt-manager
Traceback (most recent call last):
  File "/nix/store/4kl3dca1vrci6hhipnn1l699k662szbv-virt-manager-1.4.3/share/virt-manager/virt-manager", line 32, in <module>
    gi.require_version('LibvirtGLib', '1.0')
  File "/nix/store/p6fnhmmvr28ziv19c37hr9n6vkcy25an-python2.7-pygobject-3.26.1/lib/python2.7/site-packages/gi/__init__.py", line 130, in require_version
    raise ValueError('Namespace %s not available' % namespace)
ValueError: Namespace LibvirtGLib not available

Steps to reproduce

Use Nixos Unstable and add virtmanager to the list of system installed packages.

Technical details

Please run nix-shell -p nix-info --run "nix-info -m" and paste the
results.

• system: "x86_64-linux"
• host os: Linux 4.14.13, NixOS, 18.03pre125130.3a763b91963 (Impala)
• multi-user?: yes
• sandbox: no
• version: nix-env (Nix) 1.11.16
• channels(hyper): "nixos-18.03pre123638.1258d9a4914"
• channels(root): "nixos-18.03pre125130.3a763b91963"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs