Fix docs build

Avoid conflicts between apidoc generated documentation and the source
code by adding "noindex" to SPHINX_APIDOC_OPTIONS.

Signed-off-by: Dr. Jens Harbott <harbott@osism.tech>
Change-Id: Ib1498a3712ec9cfd0abcb282b093f82ba0ee8128

tox.ini

@@ -66,6 +66,9 @@ import-order-style = pep8
 application-import-names = keystoneauth1
 
 [testenv:docs]
+setenv =
+    {[testenv]setenv}
+    SPHINX_APIDOC_OPTIONS=noindex,members,undoc-members,show-inheritance
 deps =
     -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/master/upper-constraints.txt}
     -r{toxinidir}/doc/requirements.txt
@@ -75,6 +78,9 @@ commands =
     sphinx-build -W -b html -d doc/build/doctrees doc/source doc/build/html
 
 [testenv:pdf-docs]
+setenv =
+    {[testenv]setenv}
+    SPHINX_APIDOC_OPTIONS=noindex,members,undoc-members,show-inheritance
 envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
 whitelist_externals =