Fix abort with msg

Fixes:
  File "/app/helpers/template_grouping.py", line 55, in _load_group_data
    abort(Response("Plugins file doesn't exist or is invalid JSON. Manual fix is needed.", 500))
  File "/usr/local/lib/python3.8/site-packages/flask/helpers.py", line 312, in abort
    _wz_abort(code, *args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/werkzeug/exceptions.py", line 881, in abort
    _aborter(status, *args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/werkzeug/exceptions.py", line 859, in __call__
    raise HTTPException(response=code)
werkzeug.exceptions.HTTPException: ??? Unknown Error: None