/usr/share/doc/gnat-gps/users_guide/_sources/ is in gnat-gps-doc 5.3dfsg-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/doc/gnat-gps/users_guide/_sources/GPS.txt
/usr/share/doc/gnat-gps/users_guide/_sources/browsing.txt
/usr/share/doc/gnat-gps/users_guide/_sources/compilation.txt
/usr/share/doc/gnat-gps/users_guide/_sources/cross_env.txt
/usr/share/doc/gnat-gps/users_guide/_sources/debugging.txt
/usr/share/doc/gnat-gps/users_guide/_sources/editing.txt
/usr/share/doc/gnat-gps/users_guide/_sources/environment.txt
/usr/share/doc/gnat-gps/users_guide/_sources/extending.txt
/usr/share/doc/gnat-gps/users_guide/_sources/help.txt
/usr/share/doc/gnat-gps/users_guide/_sources/index.txt
/usr/share/doc/gnat-gps/users_guide/_sources/intro.txt
/usr/share/doc/gnat-gps/users_guide/_sources/license.txt
/usr/share/doc/gnat-gps/users_guide/_sources/main_window.txt
/usr/share/doc/gnat-gps/users_guide/_sources/mdi.txt
/usr/share/doc/gnat-gps/users_guide/_sources/navigation.txt
/usr/share/doc/gnat-gps/users_guide/_sources/projects.txt
/usr/share/doc/gnat-gps/users_guide/_sources/remote.txt
/usr/share/doc/gnat-gps/users_guide/_sources/searching.txt
/usr/share/doc/gnat-gps/users_guide/_sources/tools.txt
/usr/share/doc/gnat-gps/users_guide/_sources/vcs.txt