[MM3-users] HyperKitty async tasks runner: systemd qcluster service fails eventually

Ubuntu 20.04 mailman3 3.2.2-1 python3-django-hyperkitty 1.3.0-1ubuntu1

According to Hyperkitty Asynchronous tasks paragraph, we can start a qcluster systemd service file:

[Unit]
Description=HyperKitty async tasks runner
After=network.target remote-fs.target

[Service]
ExecStart=/usr/bin/django-admin qcluster --pythonpath <django_project_path> --settings settings
User=<user>
Group=<group>
Restart=always

[Install]
WantedBy=multi-user.target

Starting it works fine:

# systemctl restart qcluster
# systemctl status qcluster
● qcluster.service - HyperKitty async tasks runner
   Loaded: loaded (/etc/systemd/system/qcluster.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2019-12-04 15:09:46 CET; 2ms ago
 Main PID: 1055959 ((go-admin))
    Tasks: 0 (limit: 9284)
   Memory: 0B
   CGroup: /system.slice/qcluster.service
           └─1055959 (go-admin)

Dec 04 15:09:46 samsung4-ubuntu systemd[1]: Started HyperKitty async tasks runner.

However, the service fails after a few seconds:

# systemctl status qcluster
● qcluster.service - HyperKitty async tasks runner
   Loaded: loaded (/etc/systemd/system/qcluster.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Wed 2019-12-04 15:09:48 CET; 1min 1s ago
  Process: 1055961 ExecStart=/usr/bin/django-admin qcluster --pythonpath <django_project_path> --settings settings (code=exited, status=1/FAILURE)
 Main PID: 1055961 (code=exited, status=1/FAILURE)

Dec 04 15:09:48 samsung4-ubuntu systemd[1]: qcluster.service: Service RestartSec=100ms expired, scheduling restart.
Dec 04 15:09:48 samsung4-ubuntu systemd[1]: qcluster.service: Scheduled restart job, restart counter is at 5.
Dec 04 15:09:48 samsung4-ubuntu systemd[1]: Stopped HyperKitty async tasks runner.
Dec 04 15:09:48 samsung4-ubuntu systemd[1]: qcluster.service: Start request repeated too quickly.
Dec 04 15:09:48 samsung4-ubuntu systemd[1]: qcluster.service: Failed with result 'exit-code'.
Dec 04 15:09:48 samsung4-ubuntu systemd[1]: Failed to start HyperKitty async tasks runner.

The corresponding log file is empty and I cannot find any issue in the other logs. Any suggestion?

Also, another doc paragraph Running the task queue (required) talks about another required command "python manage.py qcluster"; so which one is it?