Error While Building Web Pages

At the end of building the web pages, I got the following error(s):

Exception occurred:
File “/home/demo/blender_docs/exts/404.py”, line 25, in html_page_context
if m and m[0] == version_nbr:
TypeError: ‘_sre.SRE_Match’ object is not subscriptable
The full traceback has been saved in /tmp/sphinx-err-l_g6docb.log, if you want to report the issue to the developers.
Please also report this if it was a user error, so that a better error message can be provided next time.
A bug report can be filed in the tracker at https://github.com/sphinx-doc/sphinx/issues. Thanks!
Makefile:92: recipe for target ‘html’ failed
make: *** [html] Error 2

I spot checked a few pages and they seem to have come out fine, but if there’s something important missing, I want to know. I was using a live version of MX Linux.

Thanks.

What python version and sphinx version are you using?