/usr/share/doc/gir1.2-unity-5.0/changelog.Debian.gz is in gir1.2-unity-5.0 7.1.4+15.10.20151002-0ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/gir1.2-unity-5.0/../libunity-protocol-private0/changelog.Debian.gz