/usr/share/doc/neutron-l2gateway-agent/changelog.Debian.gz is in neutron-l2gateway-agent 1:1.0.0-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/neutron-l2gateway-agent/../python-networking-l2gw/changelog.Debian.gz