/usr/share/doc/linux-signed-image-generic-lts-wily/changelog.gz is in linux-signed-image-generic-lts-wily 4.4.0.21.22.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/linux-signed-image-generic-lts-wily/../linux-signed-image-generic/changelog.gz