Sphinx was bumped to version 4.1.1 in upper constraints just earlier today [1]. It has broken our CloudKitty documentation build [2]:

Running Sphinx v4.1.1
loading stevedore.sphinxext

Extension error:
Could not import extension wsmeext.sphinxext (exception: cannot import name 'PyClassmember' from 'sphinx.domains.python'

Both aodh and mistral are also impacted [3].

[1] https://review.opendev.org/c/openstack/requirements/+/802179/4/upper-constraints.txt

[2] https://zuul.opendev.org/t/openstack/build/86ec39a3fc84485b8f6b1e05f94c7190

[3] https://codesearch.opendev.org/?q=wsmeext.sphinxext&i=nope&files=&excludeFiles=&repos=