/usr/share/doc/linux-image-extra-virtual-hwe-16.04-edge/changelog.gz is in linux-image-extra-virtual-hwe-16.04-edge 4.15.0.20.23.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/linux-image-extra-virtual-hwe-16.04-edge/../linux-image-extra-virtual/changelog.gz