Comment 18 for bug 2034664

Hi Angel, maybe your sources list needs to be adjusted accordingly? I have it in the sources:

apt policy gnome-shell-extension-ubuntu-dock
gnome-shell-extension-ubuntu-dock:
  Installed: 87ubuntu1
  Candidate: 87ubuntu1
  Version table:
     87ubuntu2 100
        100 http://mirror.easyname.at/ubuntu-archive mantic-proposed/main amd64 Packages
        100 http://mirror.easyname.at/ubuntu-archive mantic-proposed/main i386 Packages
 *** 87ubuntu1 500
        500 http://mirror.easyname.at/ubuntu-archive mantic/main amd64 Packages
        500 http://mirror.easyname.at/ubuntu-archive mantic/main i386 Packages
        100 /var/lib/dpkg/status

Regarding the bug, I can confirm that by removing the gnome-shell-extension-ubuntu-dock package I could get rid of those log warnings (although the ubuntu-desktop-minimal package depends on gnome-shell-extension-ubuntu-dock).