Commit bd7e62f796 disabled the
autodoc_index_modules flag for building docs but it wasn't really
necessary, that change was just to get the module index out of the main
docs page.
We want to autodoc the modules so we can view the actual module index in
the tox -d docs build results, which also tells us if we have correct
ReST format in doc strings.
Notes
-----
1. Several doc string blocks have to be fixed as part of this to get
the docs tox job to pass.
2. A docstring in vhdutilsv2 is updated to remove the math directive
since that requires the sphinx.ext.pngmath extension which requires
latex and dvipng packages from the distro - which is overkill for
what the docstring was actually doing with the math directive.
3. We exclude autodoc for tests since we don't really care about
docstrings on unit tests.
4. We exclude the nova.wsgi.nova-* modules since those won't build with
autodoc since they can't be imported (there is no
nova/wsgi/__init__.py module). We could arguably add the __init__.py
but it's not really necessary for what those scripts are used for.
5. The sphinx.ext.ifconfig extension is removed since there are no docs
that use the ifconfig directive.
6. Update the developer docs to explicitly point out that graphviz must
be installed prior to running tox -e docs.
7. Hide doc/source/api/autoindex.rst from the toctree so that we don't
regress the point of commit bd7e62f796.
8. unused_docs and exclude_trees options are removed from conf.py since
they are deprecated in Sphinx 1.2.3:
https://github.com/sphinx-doc/sphinx/blob/1.2.3/sphinx/config.py#L54
9. Fix imports for moved libvirt volume options.
Closes-Bug: #1471934
Change-Id: I946e2f89f2c9fc70e870faaf84e4a8b0fc703344
8b24bf766d