AttributeError: 'UUID' object has no attribute 'encode'

[sentry]

Sentry Issue: STUDIO-FYJ

AttributeError: 'UUID' object has no attribute 'encode'
(5 additional frame(s) were not displayed)
...
  File "django_celery_results/managers.py", line 43, in _inner
    return fun(*args, **kwargs)
  File "django_celery_results/managers.py", line 173, in store_result
    obj.save(using=using)
  File "contentcuration/models.py", line 2481, in save
    self.set_signature()
  File "contentcuration/models.py", line 2475, in set_signature
    self.signature = generate_task_signature(self.task_name, task_kwargs=self.task_kwargs, channel_id=self.channel_id)
  File "contentcuration/utils/celery/tasks.py", line 88, in generate_task_signature
    md5.update((channel_id or '').encode('utf-8'))

Pool callback raised exception: "AttributeError(\"'UUID' object has no attribute 'encode'\")"

[bjester]

I was hoping that there wasn't a need for set_signature on the TaskResult model. This perhaps came about from an enqueued task right before deploy that didn't have a signature to begin with. Good news is that the presence of this bug gives us insight into how often it occurs, if at all, and if not we can remove the model handling

[rtibbles]

Fixed in #3934