Celery command syntax has changed

[azertyfun]

Hi!

Version 1.2.0 of funkwhale bundles a new version of celery, which moves the -f <logfile> argument to the sub-command rather than making it a global argument. My funkwhale wouldn't work since the workers refused to startup because they didn't recognize -f /var/log/celery-beat.log as a valid argument in its current position.

I don't know if this fix is good enough or if you want to maintain backwards-compatibility with older versions of funkwhale? In that case I can add a check based on celery --version. I'll admit I don't know much about celery and I haven't taken the t ime to go upstream to check exactly when this broke.