/usr/share/doc/libgnatcoll-readline1.6-dev/changelog.Debian.gz is in libgnatcoll-readline1.6-dev 1.6gpl2014-9.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libgnatcoll-readline1.6-dev/../libgnatcoll1.6/changelog.Debian.gz