Is there a configuration that you have ?
In the meantime I am starting it up by hand:
/usr/local/bin/gunicorn --log-file /tmp/gunicorn.log -D --chdir /opt/alarmdecoder-webapp --worker-class=socketio.sgunicorn.GeventSocketIOWorker wsgi:application --timeout=120 --env=POLICY_SERVER=0
Here is the notice during the jessie->stretch upgrade:
gunicorn (19.6.0-3) unstable; urgency=medium
The /etc/gunicorn.d (and related usr/sbin/gunicorn{,3}-debian) scripts were
removed in 19.6.0-3 due to inflexibility, lack of documentation, not
adopted/supported upstream, did not work with virtualenvs, etc.
They were dropped prior to the stretch release to avoid having to support it
for another full release.
Users relying on this feature should invoke gunicorn manually. For an example
systemd .service file, please see the ``gunicorn-mysite.service`` file in the
gunicorn-examples package or a process manager such as runit, etc.