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

Change-Id: I8bdd2912638e497f3ade79967136d1d6924574f5

doc/requirements.txt

@@ -0,0 +1,2 @@
+sphinx!=1.6.6,!=1.6.7,>=1.6.2 # BSD
+openstackdocstheme>=1.18.1 # Apache-2.0

test-requirements.txt

@@ -12,7 +12,3 @@ oslotest>=3.2.0 # Apache-2.0
 nose>=1.3.7 # LGPL
 oslo.config>=5.1.0 # Apache-2.0
 python-openstackclient>=3.12.0 # Apache-2.0
-
-# Documentation build requirements
-sphinx!=1.6.6,>=1.6.2 # BSD
-openstackdocstheme>=1.18.1 # Apache-2.0

tox.ini

@@ -27,7 +27,11 @@ commands = flake8 {posargs}
 commands = {posargs}
 
 [testenv:docs]
-commands = python setup.py build_sphinx
+deps =
+       -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
+       -r{toxinidir}/requirements.txt
+       -r{toxinidir}/doc/requirements.txt
+commands = sphinx-build -b html doc/source doc/build/html
 
 [testenv:functional]
 # This tox env is purely to make local test development easier