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

spot on :-) Changing the permissions of /var/log/mailman3/mailmansuite.log to list:list solves this issue:

# systemctl status qcluster
● qcluster.service - HyperKitty async tasks runner
   Loaded: loaded (/etc/systemd/system/qcluster.service; enabled; vendor preset: enabled)
   Active: active (running) since Fri 2019-12-06 10:53:23 CET; 1h 33min ago
 Main PID: 1314343 (python3)
    Tasks: 8 (limit: 9284)
   Memory: 108.4M
   CGroup: /system.slice/qcluster.service
           ├─1314343 python3 /usr/bin/django-admin qcluster --pythonpath <django_project_path> --settings settings
           ├─1314370 python3 /usr/bin/django-admin qcluster --pythonpath <django_project_path> --settings settings
           ├─1314371 python3 /usr/bin/django-admin qcluster --pythonpath <django_project_path> --settings settings
           ├─1314372 python3 /usr/bin/django-admin qcluster --pythonpath <django_project_path> --settings settings
           ├─1314373 python3 /usr/bin/django-admin qcluster --pythonpath <django_project_path> --settings settings
           ├─1314374 python3 /usr/bin/django-admin qcluster --pythonpath <django_project_path> --settings settings
           ├─1314375 python3 /usr/bin/django-admin qcluster --pythonpath <django_project_path> --settings settings
           └─1314376 python3 /usr/bin/django-admin qcluster --pythonpath <django_project_path> --settings settings

Dec 06 10:53:23 samsung4-ubuntu systemd[1]: Started HyperKitty async tasks runner.
Dec 06 10:53:24 samsung4-ubuntu django-admin[1314343]: 10:53:24 [Q] INFO Q Cluster-1314343 starting.
Dec 06 10:53:24 samsung4-ubuntu django-admin[1314343]: 10:53:24 [Q] INFO Process-1:1 ready for work at 1314371
Dec 06 10:53:24 samsung4-ubuntu django-admin[1314343]: 10:53:24 [Q] INFO Process-1:2 ready for work at 1314372
Dec 06 10:53:24 samsung4-ubuntu django-admin[1314343]: 10:53:24 [Q] INFO Process-1:3 ready for work at 1314373
Dec 06 10:53:24 samsung4-ubuntu django-admin[1314343]: 10:53:24 [Q] INFO Process-1:4 ready for work at 1314374
Dec 06 10:53:24 samsung4-ubuntu django-admin[1314343]: 10:53:24 [Q] INFO Process-1:5 monitoring at 1314375
Dec 06 10:53:24 samsung4-ubuntu django-admin[1314343]: 10:53:24 [Q] INFO Process-1 guarding cluster at 1314370
Dec 06 10:53:24 samsung4-ubuntu django-admin[1314343]: 10:53:24 [Q] INFO Process-1:6 pushing tasks at 1314376
Dec 06 10:53:24 samsung4-ubuntu django-admin[1314343]: 10:53:24 [Q] INFO Q Cluster-1314343 running.

It seems that this file is created during the installation of one of mailman3 binary packages.