Can someone help with this and tell me what it means?

[xxwynterxx]

Last Module Called: whims_tracker.py Last Function Called: _generate_whim_buckets_for_type_and_whimset Error message: Exception raised while trying to run a test event in test_events.py: (AttributeError: 'NoneType' object has no attribute 'guid64'), CategoryID: whims_tracker:1354