After Sphinx 3.5.0 was updated to release 3.5.0 few hours ago all pywikibot-core-tox-doc-docker tests fails:
11:12:45 Extension error (sphinx.ext.viewcode): 11:12:45 Handler <function env_purge_doc at 0x7fb96305e6a8> for event 'env-purge-doc' threw an exception (exception: 'bool' object is not iterable) 11:12:46 ERROR: InvocationError for command /src/.tox/doc/bin/sphinx-build -M html ./docs ./docs/_build (exited with code 2)