AttributeError: 'CustomTaskMetadata' object has no attribute 'task_name'

[bjester]

Observed behavior

Requests to the sync endpoint fail when custom tasks have been invoked
Occurring on unstable branch

Traceback (most recent call last):
  File "/home/bjester/Projects/learningequality/pyenv/versions/studio-3.9.13/lib/python3.9/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/home/bjester/Projects/learningequality/pyenv/versions/studio-3.9.13/lib/python3.9/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/bjester/Projects/learningequality/pyenv/versions/studio-3.9.13/lib/python3.9/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/home/bjester/Projects/learningequality/pyenv/versions/studio-3.9.13/lib/python3.9/site-packages/django/views/generic/base.py", line 70, in view
    return self.dispatch(request, *args, **kwargs)
  File "/home/bjester/Projects/learningequality/pyenv/versions/studio-3.9.13/lib/python3.9/site-packages/newrelic/hooks/component_djangorestframework.py", line 28, in _nr_wrapper_APIView_dispatch_
    return wrapped(*args, **kwargs)
  File "/home/bjester/Projects/learningequality/pyenv/versions/studio-3.9.13/lib/python3.9/site-packages/rest_framework/views.py", line 509, in dispatch
    response = self.handle_exception(exc)
  File "/home/bjester/Projects/learningequality/pyenv/versions/studio-3.9.13/lib/python3.9/site-packages/rest_framework/views.py", line 469, in handle_exception
    self.raise_uncaught_exception(exc)
  File "/home/bjester/Projects/learningequality/pyenv/versions/studio-3.9.13/lib/python3.9/site-packages/rest_framework/views.py", line 480, in raise_uncaught_exception
    raise exc
  File "/home/bjester/Projects/learningequality/pyenv/versions/studio-3.9.13/lib/python3.9/site-packages/rest_framework/views.py", line 506, in dispatch
    response = handler(request, *args, **kwargs)
  File "/home/bjester/Projects/learningequality/studio2/contentcuration/contentcuration/viewsets/sync/endpoint.py", line 179, in post
    response_payload.update(self.return_tasks(request, channel_revs))
  File "/home/bjester/Projects/learningequality/studio2/contentcuration/contentcuration/viewsets/sync/endpoint.py", line 151, in return_tasks
    "task_name": custom_task.task_name,
AttributeError: 'CustomTaskMetadata' object has no attribute 'task_name'

Expected behavior

Endpoint properly returns task results