/usr/share/doc/linux-image-extra-3.13.0-52-generic/changelog.Debian.gz is in linux-image-extra-3.13.0-52-generic 3.13.0-52.86.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/linux-image-extra-3.13.0-52-generic/../linux-image-3.13.0-52-generic/changelog.Debian.gz