this is a stack of 3 small revisions
- add a hack in conf.py to make httpdomain routing table referencable
this aims at eliminating a warning generated by sphinx-build on swh-web's
index, due to the presence of an explicit link to the http-routingtable.html
file (which does not exists at that time, thus generated a warning).
This should be killed once
is accepted and released.
- make it possible to set the SPHINXOPTS env var when building the doc with tox
This will allow the CI to run the building job with sphinx options like
-W (aka "turn warnings into errors").
- docs: prevent a 'file non included in a toctree' warning
related to T1331