Dear Maintainer,

   * What led up to the situation?
After a dist-upgrade, gnome shell got removed. After gnome-shell became
available for installation again, it installs cleanly again, but segfaults when
starting. Relevant error messare from /var/log/message:

Aug 28 19:32:56 della kernel: [149450.625143] gnome-shell[27088]: segfault at
64 ip 00007f7502408440 sp 00007fff5c4861c8 error 4 in
libcogl.so.20.3.0[7f75023b7000+a1000]
Aug 28 19:32:56 della gnome-session[26954]: gnome-session[26954]: WARNING:
Application 'gnome-shell.desktop' killed by signal 11
Aug 28 19:32:56 della kernel: [149450.793560] gnome-shell[27103]: segfault at
64 ip 00007ff8bea28440 sp 00007ffd76e818c8 error 4 in
libcogl.so.20.3.0[7ff8be9d7000+a1000]
Aug 28 19:32:56 della gnome-session[26954]: gnome-session[26954]: WARNING:
Application 'gnome-shell.desktop' killed by signal 11
Aug 28 19:32:56 della gnome-session[26954]: gnome-session[26954]: WARNING: App
'gnome-shell.desktop' respawning too quickly


   * What exactly did you do (or not do) that was effective (or
     ineffective)?
I do not know how to prevent gnome-shell from using libcogl in order to make
sure that it is indeed a libcogl problem rahter than a gnome-shell roblem.