Error when running create_dataset_stats script

[sirex]

When I run:

python create_dataset_stats.py

got following error:

Traceback (most recent call last):
  File "create_dataset_stats.py", line 239, in <module>
    run(main)
  File "create_dataset_stats.py", line 181, in main
    stats = _update_dataset_maturity_level_and_object_count_stats(
  File "create_dataset_stats.py", line 139, in _update_dataset_maturity_level_and_object_count_stats
    data = json.loads(res.content)
  File "json/__init__.py", line 346, in loads
    return _default_decoder.decode(s)
  File "json/decoder.py", line 337, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "json/decoder.py", line 355, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)