No protocol specified in Evince

The evince pdf viewer under Ubuntu 14.04 LTS didn’t work anymore, after I have moved my home directory from /home to /data/home

A symlink wasn’t sufficient.

After looking up https://bugs.launchpad.net/ubuntu/+source/evince/+bug/1433165 the solution is simply to run

sudo dpkg-reconfigure apparmor

and configure the new home directory to /data/home/. The last / is important!