Follow the new PTI for document build

For compliance with the Project Testing Interface as described in:

https://governance.openstack.org/tc/reference/project-testing-interface.html

For more detials information, please refer to:

http://lists.openstack.org/pipermail/openstack-dev/2017-December/125710.html

Change-Id: I673214c9e231294e7d5eb473232e2a611e219b47

setup.cfg

@@ -36,13 +36,6 @@ stevedore.test.extension =
     e1 = stevedore.tests.test_extension:BrokenExtension
     e2 = stevedore.tests.notfound:UnimportableExtension
 
-
-[build_sphinx]
-all_files = 1
-build-dir = doc/build
-source-dir = doc/source
-warning-is-error = 1
-
 [pbr]
 warnerrors = True
 

tox.ini

@@ -31,7 +31,7 @@ commands =
 
 [testenv:docs]
 deps = -r{toxinidir}/doc/requirements.txt
-commands = python setup.py build_sphinx
+commands = sphinx-build -W -b html doc/source doc/build/html
 
 [flake8]
 ignore = E251