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