Selecting videos results in errors

We're currently evaluating tools to label video data, including eva... however, while we got it running quickly (which was really nice), the tool doesn't do anything when selecting a video but just shows some errors on the cli:
[2020-03-09 17:01:12] "POST /upload/testabcde/ HTTP/1.1" 200 73
[2020-03-09 17:01:12] Internal Server Error: /upload/testabcde/done/
Traceback (most recent call last):
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/kombu/utils/objects.py", line 42, in __get__
    return obj.__dict__[self.__name__]
KeyError: 'backend'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/django/core/handlers/exception.py", line 41, in inner
    response = get_response(request)
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/django/core/handlers/base.py", line 249, in _legacy_get_response
    response = self._get_response(request)
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/django/core/handlers/base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/django/core/handlers/base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/django/views/generic/base.py", line 68, in view
    return self.dispatch(request, *args, **kwargs)
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/django/views/generic/base.py", line 88, in dispatch
    return handler(request, *args, **kwargs)
  File "/home/username/sourcecode/thirdParty/eva/annotator/views.py", line 326, in post
    task = chain(extract_frames.s() | create_cache_task.s())(video.id)
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/celery/canvas.py", line 530, in __call__
    return self.apply_async(args, kwargs)
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/celery/canvas.py", line 557, in apply_async
    dict(self.options, **options) if options else self.options))
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/celery/canvas.py", line 573, in run
    task_id, group_id, chord,
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/celery/canvas.py", line 666, in prepare_steps
    root_id=root_id, group_id=group_id, chord=chord_body,
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/celery/canvas.py", line 281, in freeze
    return self.AsyncResult(tid)
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/celery/app/task.py", line 749, in AsyncResult
    return self._get_app().AsyncResult(task_id, backend=self.backend,
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/celery/app/task.py", line 992, in backend
    return self.app.backend
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/kombu/utils/objects.py", line 44, in __get__
    value = obj.__dict__[self.__name__] = self.__get(obj)
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/celery/app/base.py", line 1196, in backend
    return self._get_backend()
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/celery/app/base.py", line 914, in _get_backend
    self.loader)
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/celery/app/backends.py", line 70, in by_url
    return by_name(backend, loader), url
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/celery/app/backends.py", line 50, in by_name
    cls = symbol_by_name(backend, aliases)
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/kombu/utils/imports.py", line 56, in symbol_by_name
    module = imp(module_name, package=package, **kwargs)
  File "/home/username/anaconda3/lib/python3.7/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 724, in exec_module
  File "<frozen importlib._bootstrap_external>", line 860, in get_code
  File "<frozen importlib._bootstrap_external>", line 791, in source_to_code
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/username/sourcecode/thirdParty/eva/venv/lib/python3.7/site-packages/celery/backends/redis.py", line 22
    from . import async, base
                      ^
SyntaxError: invalid syntax
Some system info:
Python 3.7.3 RedHat 7 Linux kernel 3.10.0-1062.12.1.el7.x86_64
Ericsson / eva

Selecting videos results in errors #5
