From the recent changelog of systemd:
systemd (239-3) unstable; urgency=medium
* Revert "systemctl: when removing enablement or mask symlinks,
cover both /run and /etc"
We currently have packages in the archive which use "systemctl
--runtime unmask" and are broken by this change. This is a intermediate
step until it is clear whether upstream will revert this commit or
whether we will have to update affected packages to deal with this
changed behaviour.
See #902287 and https://github.com/systemd/systemd/issues/9393
-- Michael Biebl <bi...@debian.org> Wed, 27 Jun 2018 14:46:06 +0200
Looks like this package is also affected by #902287
