Comment 2 for bug 1241487

From VarLogDistUpgradeAptlog.txt we end up in a loop of this:

Investigating (1) libgdm [ amd64 ] < none -> 3.8.4-0ubuntu2 > ( universe/libs )
Broken libgdm:amd64 Breaks on gdm [ amd64 ] < 3.6.1-0ubuntu4 -> 3.8.4-0ubuntu2 > ( universe/gnome ) (< 3.8.3-3~)
  Considering gdm:amd64 0 as a solution to libgdm:amd64 1
  Upgrading gdm:amd64 due to Breaks field in libgdm:amd64
Investigating (1) gdm [ amd64 ] < 3.6.1-0ubuntu4 -> 3.8.4-0ubuntu2 > ( universe/gnome )
Broken gdm:amd64 Depends on gnome-shell [ amd64 ] < none -> 3.8.4-0ubuntu5 > ( universe/gnome )
  Considering gnome-shell:amd64 0 as a solution to gdm:amd64 0
  Holding Back gdm:amd64 rather than change gnome-shell:amd64