/usr/share/info/gnat_ugn_unw.info.gz is in gnat-doc 4.6ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/info/gnat_ugn_unw-4.6.info.gz
/usr/share/info/gnat_ugn_unw-4.6.info.gz