Add specific doc build option and gate on warnings

Add doc venv to align with other OpenStack projejcts (such as keystone,
heat and nova-specs) who are using 'docs' for there doc builds.  Also
enable warnerrors in pbr to raise an error if there are any docs
formatting warnings.

Change-Id: Ifa31edf3c3392106a8aa1352bdd557bde2f1b9a1

doc/source/conf.py

@@ -156,7 +156,7 @@ modindex_common_prefix = ['marconi.']
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['_static']
+html_static_path = []
 
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.

setup.cfg

@@ -87,3 +87,6 @@ cover-inclusive = true
 ;
 ; detailed-errors = 1
 
+
+[pbr]
+warnerrors = True

tox.ini

@@ -46,6 +46,9 @@ commands =
 [testenv:venv]
 commands = {posargs}
 
+[testenv:docs]
+commands = python setup.py build_sphinx
+
 [flake8]
 exclude = .venv*,.git,.tox,dist,doc,*openstack/common*,*lib/python*,*.egg,.update-venv