How to fix a bug, using the example of Quod Libet empty panes on Gentoo GNU/Linux (bug solving process)

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For a few days now my Quod Libet has been broken, showing only empty space instead of information panes.


I investigated halfheartedly, but did not find the cause with quick googling. Today I decided to change that. I document my path here, because I did not yet write about how I actually tackle problems like these - and I think I would have profited from having a writeup like this when I started, instead of having to learn it by trial-and-error.

Update: Quodlibet 2.6.3 is now in the Gentoo portage tree - using my ebuild. The update works seamlessly. So to get your Quodlibet 2.5 running again, just call emerge =media-sound/quodlibet-2.6.3 =media-plugins/quodlibet-plugins-2.6.3. Happy Hacking!

Update: I got a second reply in the bug tracker which solved the plugins problem: I had user-plugins which require Quod Libet 3. Solution: mv ~/.quodlibet/plugins ~/.quodlibet/plugins.for-ql3. Quod Libet works completely again.

Solution for the impatient: Update to Quod Libet 2.5.1. In Gentoo that’s easy.

1 Gathering Information

As starting point I installed the Quod Libet plugins (media-libs/quodlibet-plugins), thinking that the separation between plugins and mediaplayer might not be perfect. That did not fix the problem, but a look at the plugin listing gave me nice backtraces:


And these actually show the reason for the breakage: Cannot import GTK:

Traceback (most recent call last):
  File "/home/arne/.quodlibet/plugins/songsmenu/", line 51, in <module>
    from gi.repository import Gtk, Pango, GLib, Gdk, GdkPixbuf
  File "/usr/lib64/python2.7/site-packages/gi/", line 27, in <module>
    from ._gi import _API, Repository
ImportError: cannot import name _API

Let’s look which package this file belongs to:

equery belongs /usr/lib64/python2.7/site-packages/gi/
 * Searching for /usr/lib64/python2.7/site-packages/gi/ ... 
dev-python/pygobject-3.8.3 (/usr/lib64/python2.7/site-packages/gi/

So I finally have an answer: pygobject changed the API. Can’t be hard to fix… (a realization process follows)

2 The solution-hunting process

  • let’s check the Gentoo forums for pygobject
  • pygobject now pulls systemd??? - and they wonder why I’m pissed off by systemd: hugely invasive changes just for some small packages… KDE gets rid of the monolithic approach, and now Gnome starts it, just much more invasive into the basic structure of all distros?
  • set the USE flag -systemd to avoid systemd (why didn’t I have that yet? I guess I did not expect that Gentoo would push that on me…)
  • check when I updated pygobject:
qlop -l pygobject
Thu Dec  5 00:26:27 2013 >>> dev-python/pygobject-3.8.3
  • a week ago - that fits the timeframe. Damn… pygobject-3.8.3, you have to go.
echo =dev-python/pygobject-3.8.3 >> /usr/portage/package.mask
emerge -u pygobject
  • hm, no, the backtrace was for the plugin, but when I start Quod Libet from the shell, I see this:
LANG=C quodlibet
/usr/lib64/python2.7/site-packages/quodlibet/qltk/ GtkWarning: Unable to locate theme engine in module_path: "clearlooks",
  _label = gtk.Label().create_pango_layout("")
  • emerge x11-themes/clearlooks-phenix to get clearlooks again. Looks nicer now, but still not fixed.


  • back to the drawing board. Let’s tackle this pygobject thing: emerge -C =dev-python/pygobject-3.8.3/, emerge -1 =dev-python/pygobject-2.28.6-r55.
  • not fixed. OK… let’s report a bug: empty information panes (screenshots attached).

3 The core solution

In the bug report at Quod Libet I got a reply: Known issue with quodlibet 2.5 “which triggered a bug in a recent pygtk release, resulting in lists not showing”. The plugins seem to be unrelated. Solution to my immediate problem: Update to 2.5.1. That’s not yet in gentoo, but this is easy to fix:

cd /usr/portage/media-sound/
# create the category in my local portage overlay, defined as
# PORTAGE_OVERLAY=/usr/local/portage in /etc/make.conf
mkdir -p /usr/local/portage/media-sound
# copy over the quodlibet directory, keeping the permissiong with -p
cp -rp quodlibet /usr/local/portage/media-sound
# most times it is enough to simply rename the ebuild to the new version
cd /usr/local/portage/media-sound/quodlibet
mv quodlibet-2.5.ebuild quodlibet-2.5.1.ebuild
# now prepare all the metadata portage needs - this requires
# app-portage/gentoolkit
ebuild quodlibet-2.5.1.ebuild digest compile 
# now it's prepared for the package manager. Just update it as usual:
emerge -u quodlibet

I wrote the solution in the Gentoo bug report. I should also state, that the gentoo package for Quod Libet is generally out of date (releases 2.6.3 and 3.0.2 are not yet in the tree).

Quod Libet works again.


As soon as the ebuild in the portage tree is renamed, Quod Libet should work again for all Gentoo users.

The plugins still need to be fixed, but I’ll worry about that later.

4 Conclusion

Solving the core problem took me some time, but it wasn’t really complicated. The part of the solution process which got me forward boils down to:

  • checking the project bug tracker,
  • checking the distribution bug tracker,
  • reporting a bug for the project with the information I could gather - including screenshots (or anything else which shows the problem directly - see How to Report Bugs Effectively for hints on that), and
  • checking the reported bug again a few hours or days later - and synchronizing the information between the project bug tracker and the distribution bug tracker to help fixing the bug for all users of the distribution and of other distributions.

And that’s it: To get something working again, check the bug trackers, report bugs and help synchronizing bug tracker info.

2013-12-11-quod-libet-broken.png49.59 KB
2013-12-11-quod-libet-broken-clearlooks.png50.44 KB
2013-12-11-quod-libet-broken-plugins.png27.47 KB
2013-12-11-quod-libet-fixed.png85.61 KB
2013-12-11-Mi-quodlibet-broken.org7.11 KB
2013-12-11-Mi-quodlibet-broken.pdf419.37 KB

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