An unknown exception was thrown during indexing.

[RIKnight]

This is my first attempt to use Sourcetrail. It failed with a spectacularly uninformative error message:
"An unknown exception was thrown during indexing."
I was attempting to index the code from the open source repository at https://github.com/FDA/openfda.
I pulled this repo into a local directory on my machine, then tried to index it using Sourcetrail.
The OpenFDA code uses Python more than any other language, so I told Sourcetrail that it was a "Python source group". I also told it to look for .py, .html, .js, .sh, and .json files, since those are all included in the repo.
I ran the indexing, which went on for 20+ minutes before crashing with this veritably useless error message.
What does it mean?

[RIKnight]

log_2021-10-03_19-47-25.txt