/usr/share/doc/libvisp-io3.1-dbg/changelog.Debian.gz is in libvisp-io3.1-dbg 3.1.0-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libvisp-io3.1-dbg/../libvisp-core3.1/changelog.Debian.gz