/usr/share/doc/libpion-common-4.0-dbg/changelog.Debian.gz is in libpion-common-4.0-dbg 4.0.7+dfsg-3.1ubuntu4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libpion-common-4.0-dbg/../libpion-common-4.0/changelog.Debian.gz