/usr/share/doc/percona-xtradb-cluster-server/changelog.Debian.gz is in percona-xtradb-cluster-server 5.5.34-25.9+dfsg-0ubuntu4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/percona-xtradb-cluster-server/../percona-xtradb-cluster-client-5.5/changelog.Debian.gz