/usr/share/doc/libptscotch-5.1/changelog.Debian.gz is in libptscotch-5.1 5.1.12b.dfsg-2build4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libptscotch-5.1/../libscotch-5.1/changelog.Debian.gz