/usr/share/doc/libcholmod1.7.1/changelog.Debian.gz is in libcholmod1.7.1 1:3.4.0-2ubuntu3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libcholmod1.7.1/../libamd2.2.0/changelog.Debian.gz