Changed `""` into `''` to pass an empty token. Seems to be linked to this warning:
```
/opt/conda/lib/python3.8/site-packages/traitlets/traitlets.py:2195: FutureWarning: Supporting extra quotes around Unicode is deprecated in traitlets 5.0. Use '' instead of "''" – or use CUnicode.
```

Added debug information (ouput of the command line).