/usr/share/doc/mysql-client-5.5/changelog.Debian.gz is in mysql-client-5.5 5.5.54-0ubuntu0.12.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/mysql-client-5.5/../mysql-client-core-5.5/changelog.Debian.gz