/usr/share/doc/linux-image-extra-4.4.0-137-generic/changelog.Debian.gz is in linux-image-extra-4.4.0-137-generic 4.4.0-137.163~14.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/linux-image-extra-4.4.0-137-generic/../linux-image-4.4.0-137-generic/changelog.Debian.gz