/usr/share/man/man1/aubusy.1.gz is in aufs-tools 1:4.9+20170918-1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man1/../man5/aufs.5.gz
/usr/share/man/man1/../man5/aufs.5.gz