Follow the new PTI for document build

For compliance with the Project Testing Interface as described in:
[1] https://governance.openstack.org/tc/reference/project-testing-interface.html
[2] http://lists.openstack.org/pipermail/openstack-dev/2017-December/125710.html

Change-Id: I001f8d12a277e520af85ca18a27ff90b3cd98ae2
Closes-Bug: #1755190

doc/requirements.txt

@@ -0,0 +1,5 @@
+doc8>=0.6.0 # Apache-2.0
+sphinx!=1.6.6,!=1.6.7,>=1.6.2 # BSD
+openstackdocstheme>=1.18.1 # Apache-2.0
+os-api-ref>=1.4.0 # Apache-2.0
+reno>=2.5.0 # Apache-2.0

test-requirements.txt

@@ -5,22 +5,16 @@
 # Despite above warning added by global sync process, please use
 # ascii betical order.
 coverage!=4.4,>=4.0 # Apache-2.0
-doc8>=0.6.0 # Apache-2.0
 fixtures>=3.0.0 # Apache-2.0/BSD
 hacking!=0.13.0,<0.14,>=0.12.0 # Apache-2.0
 mock>=2.0.0 # BSD
 python-subunit>=1.0.0 # Apache-2.0/BSD
 python-tackerclient>=0.8.0 # Apache-2.0
 ordereddict>=1.1 # MIT
-sphinx!=1.6.6,!=1.6.7,>=1.6.2 # BSD
 oslotest>=3.2.0 # Apache-2.0
 os-testr>=1.0.0 # Apache-2.0
 tempest>=17.1.0 # Apache-2.0
-os-api-ref>=1.4.0 # Apache-2.0
 testrepository>=0.0.18 # Apache-2.0/BSD
 testtools>=2.2.0 # MIT
 WebTest>=2.0.27 # MIT
 python-barbicanclient>=4.5.2 # Apache-2.0
-
-# releasenotes
-reno>=2.5.0 # Apache-2.0

tox.ini

@@ -46,6 +46,8 @@ basepython = python3.5
 commands = oslo_debug_helper {posargs}
 
 [testenv:pep8]
+deps = -r{toxinidir}/doc/requirements.txt
+       -r{toxinidir}/test-requirements.txt
 basepython = python2.7
 commands =
   flake8
@@ -58,20 +60,21 @@ whitelist_externals = bash
 commands = python ./tools/check_i18n.py ./tacker ./tools/i18n_cfg.py
 
 [testenv:docs]
-basepython = python2.7
+deps = -r{toxinidir}/doc/requirements.txt
 commands =
-    doc8 -e .rst doc/source/ CONTRIBUTING.rst HACKING.rst README.rst TESTING.rst
-    python setup.py build_sphinx
+  sphinx-build -b html doc/source doc/build/html
 
 [testenv:api-ref]
 # This environment is called from CI scripts to test and publish
 # the API Ref to developer.openstack.org.
+deps = -r{toxinidir}/doc/requirements.txt
 commands =
   rm -rf api-ref/build
   sphinx-build -W -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html
 whitelist_externals = rm
 
 [testenv:releasenotes]
+deps = -r{toxinidir}/doc/requirements.txt
 commands =
   sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html