/usr/share/doc/mir-demos/changelog.Debian.gz is in mir-demos 0.21.0+16.04.20160330-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/mir-demos/../libmircommon5/changelog.Debian.gz
/usr/share/doc/mir-demos/../libmircommon5/changelog.Debian.gz