Update .zuul.yaml to use PTI job, update tox.ini to use the common way
to run sphinx, update setup.cfg for handling warnings as errors.
Add new docs target to tox.ini and make it default target, the target is
needed by CI scripts.
Note that ossa does not work with python3, so the docs environment does
not use basepython. This needs a rework of doc/source/_exts/vmt.py.
This is a mechanically generated patch to complete step 1 of moving
the zuul job settings out of project-config and into each project
Because there will be a separate patch on each branch, the branch
specifiers for branch-specific jobs have been removed.
Because this patch is generated by a script, there may be some
cosmetic changes to the layout of the YAML file(s) as the contents are
See the python3-first goal document for details: