/usr/share/doc/libgnatcoll16.1.0-dev/changelog.Debian.gz is in libgnatcoll16.1.0-dev 17.0.2017-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libgnatcoll16.1.0-dev/../libgnatcoll16.1.0/changelog.Debian.gz