Hi, It seems the openstack-tox-docs job is broken in some projects because of the following change made in Sphinx >= 5.0.0 . https://github.com/sphinx-doc/sphinx/commit/a3d09835522e6487cf93dcc871179db8... We currently have Sphinx 4.5.0 in upper-constraints.txt but some projects (eg. Heat, Nova, Neutron) are using only their own docs-constraints.txt and pull the latest version which is 5.0.1 . IMO we need to fix the problem by the following two steps, but I'd appreciate if anybody can share a better idea. 1. Update tox.ini to honor upper-constraints.txt. This is needed in master and stable/branches as well. 2. Update docs/source/conf.py to hard-code the language parameter to 'en'. This is required in master so that we can bump the upper version later. Thank you, Takashi Kajinami