gnome-tweaks cannot run on fedora-29 template

[tquest1]

Qubes OS version:

R4.0

Affected component(s):

qubes-template-fedora-29 from templates-itl-testing

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Steps to reproduce the behavior:

Install and try to start gnome-tweaks

Expected behavior:

start successfully

Actual behavior:

$ gnome-tweaks
WARNING : Shell not installed or running
WARNING : Error detecting shell
Traceback (most recent call last):
  File "/usr/lib/python3.7/site-packages/gtweak/tweaks/tweak_group_shell_extensions.py", line 217, in __init__
    raise Exception("Shell not running or DBus service not available")
Exception: Shell not running or DBus service not available
Traceback (most recent call last):
  File "/usr/lib/python3.7/site-packages/gtweak/app.py", line 30, in do_activate
    self.win = Window(self, model)
  File "/usr/lib/python3.7/site-packages/gtweak/tweakview.py", line 38, in __init__
    self._model.load_tweaks(self)
  File "/usr/lib/python3.7/site-packages/gtweak/tweakmodel.py", line 104, in load_tweaks
    mods = __import__("gtweak.tweaks", globals(), locals(), tweak_files, 0)
  File "/usr/lib/python3.7/site-packages/gtweak/tweaks/tweak_group_general.py", line 14, in <module>
    _shell_not_ubuntu = _shell.mode != 'ubuntu'
AttributeError: 'NoneType' object has no attribute 'mode'

General notes:

gnome-tweaks (or the previous gnome-tweak-tool) has successfully installed & run on previous recent versions of Qubes fedora templates without any problems.
It makes it much easier to install or tryout different gtk / icon themes & fonts & font-aliasing.

As a workaround I run this from the terminal:

gsettings set org.gnome.desktop.interface gtk-theme Arc && gsettings set org.gnome.desktop.interface icon-theme Papirus && gsettings set org.gnome.settings-daemon.plugins.xsettings antialiasing 'rgba' && gsettings set org.gnome.settings-daemon.plugins.xsettings hinting 'slight' && gsettings set org.gnome.desktop.interface font-name 'Noto Sans 11' && gsettings set org.gnome.desktop.interface document-font-name 'Noto Sans Regular 11' && gsettings set org.gnome.desktop.interface monospace-font-name 'Source Code Pro Medium 13'

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Related issues:

[andrewdavidwong]

Not sure if this is actually a Qubes issue.

[marmarek]

Looks like gnome-tweaks doesn't like to be started outside of GNOME. But according to project page it should be supported:

Tweaks is designed for GNOME Shell but can be used in other desktops. A few features will be missing when Tweaks is run on a different desktop.

Reported upstream: https://gitlab.gnome.org/GNOME/gnome-tweaks/issues/192