Bug#1118500: liferea: not compatible with pygobject >= 3.52

[Simon McVittie]

Package: liferea
Version: 1.16.1+ds-2
Severity: important
Tags: upstream forky sid
X-Debbugs-Cc: pygobject at packages.debian.org
Control: block 1118363 by -1

pygobject >= 3.52 (available in experimental) has switched from 
libgirepository-1.0 to libgirepository-2.0 as its way to access GObject 
libraries such as GTK.

libgirepository-1.0 and libgirepository-2.0 can be installed on the same 
system, but they cannot both be used within the same process, because 
they both register a GObject type named "GIRepository". This means that 
pygobject, libpeas, and apps like liferea all need to agree on which 
version they are going to use.

As a result we need to do a coordinated transition from:

    pygobject 3.50.x
    older libpeas
    older pygobject-dependent apps

to:

    pygobject >= 3.52
    libpeas >= 1.36.0-6~
    newer pygobject-dependent apps

The symptom is that if you start liferea on a system that has the versions of 
pygobject and libpeas from experimental:

    sudo apt install libgirepository-2.0-0 liferea
    sudo apt install python3-gi{,-cairo}/experimental libpeas-1.0-0/experimental gir1.2-peas-1.0/experimental
    liferea

it won't start, with messages similar to those below:

>/usr/lib/python3/dist-packages/gi/module.py:50: Warning: cannot register existing type 'GIRepository'
>  repository = Repository.get_default()
>/usr/lib/python3/dist-packages/gi/module.py:50: Warning: g_once_init_leave_pointer: assertion 'result != 0' failed
>  repository = Repository.get_default()
>/usr/lib/python3/dist-packages/gi/module.py:50: Warning: g_object_new_with_properties: assertion 'G_TYPE_IS_OBJECT (object_type)' failed
>  repository = Repository.get_default()
>/usr/lib/python3/dist-packages/gi/module.py:50: Warning: g_object_add_weak_pointer: assertion 'G_IS_OBJECT (object)' failed
>  repository = Repository.get_default()
>/usr/lib/python3/dist-packages/gi/module.py:50: Warning: g_once_init_leave: assertion 'result != 0' failed
>  repository = Repository.get_default()
>/usr/lib/python3/dist-packages/gi/module.py:50: Warning: g_object_ref: assertion 'G_IS_OBJECT (object)' failed
>  repository = Repository.get_default()

For GNOME apps, a similar issue is fixed in the latest experimental 
uploads of eog, gedit, rhythmbox and totem, but now we need to do the 
same for non-GNOME apps as well.

I'm preparing patches for this, but they are not ready yet 
(see https://salsa.debian.org/debian/liferea/-/merge_requests/5 for 
progress). Initially, these changes will need to be uploaded to 
experimental, either by a maintainer or as an NMU. Optionally a 
maintainer could update to the latest 1.16.x release from upstream 
instead of backporting patches (but as a non-maintainer I don't plan to 
propose that change myself).

After we get a transition slot from the release team, we will need to 
include liferea in a coordinated upload to unstable of pygobject, libpeas 
and several affected apps. Again, this can either be a maintainer upload 
or an NMU.

Thanks,
    smcv