I managed to reproduce this rejection after setting user-authority-in-system-dir=true in lightdm.conf with apparmor 2.8.95~2430-0ubuntu5.1 from trusty-updates. I verified that with apparmor 2.8.95~2430-0ubuntu5.2 in trusty-proposed, the rejection on the Xauthority file no longer appears. Marking verification-done.
I managed to reproduce this rejection after setting user-authority- in-system- dir=true in lightdm.conf with apparmor 2.8.95~ 2430-0ubuntu5. 1 from trusty-updates. I verified that with apparmor 2.8.95~ 2430-0ubuntu5. 2 in trusty-proposed, the rejection on the Xauthority file no longer appears. Marking verification-done.