/usr/share/doc/libpetsc3.6.2-dev/changelog.Debian.gz is in libpetsc3.6.2-dev 3.6.2.dfsg1-3ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libpetsc3.6.2-dev/../libpetsc3.6/changelog.Debian.gz