python-fsleyes-widgets fails to build with Sphinx 2, because Sphinx itself no longer provides sphinx_rtd_theme.
Also, there's a deprecation warning:
/usr/lib/python3.8/site-packages/sphinx/events.py:76: RemovedInSphinx30Warning: autodoc_default_flags is now deprecated. Please use autodoc_default_options instead.
This will block the rebuild with Python 3.8.
We plan to start 3.8 rebuilds in a side tag this week. The sooner the builds are done, the sooner the side tag can be merged back to rawhide. If the side tag is "open" for too long, it tends to diverge and the merge is more problematic. We usually decide to merge it even if some packages fail to build to prevent that. Once we do, packages that failed to rebuild will fail to install. If you are OK with that, it blocks nothing.