Bug#1118501: entangle: not compatible with pygobject >= 3.52

[Simon McVittie]

Package: entangle
Version: 3.0-5
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 entangle 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 entangle on a system that has the versions of 
pygobject and libpeas from experimental:

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

    (in the GUI) menu -> Preferences

the preferences dialog will not open, with messages like these:

>(entangle:16066): GLib-GObject-CRITICAL **: 12:52:53.847: cannot register existing type 'GIRepository'
>(entangle:16066): GLib-CRITICAL **: 12:52:53.847: g_once_init_leave_pointer: assertion 'result != 0' failed
>(entangle:16066): GLib-GObject-CRITICAL **: 12:52:53.847: g_object_new_with_properties: assertion 'G_TYPE_IS_OBJECT (object_type)' failed
>(entangle:16066): GLib-GObject-CRITICAL **: 12:52:53.847: g_object_add_weak_pointer: assertion 'G_IS_OBJECT (object)' failed
>(entangle:16066): GLib-CRITICAL **: 12:52:53.847: g_once_init_leave: assertion 'result != 0' failed
>(entangle:16066): GLib-GObject-CRITICAL **: 12:52:53.847: g_object_ref: assertion 'G_IS_OBJECT (object)' failed

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 expect that the necessary changes for this will be similar to those in 
the experimental versions of eog, gedit, rhythmbox and totem, and 
proposed for eom (#1118496) and pluma (#1118497). Initially, these 
changes will need to be uploaded to experimental, either by a maintainer 
or as an NMU.

After we get a transition slot from the release team, we will need to 
include entangle 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