Separate doc build requirements

This commit separates the doc build requirements because the latest
sphinx doesn't work on python2.7. And we don't need doc related modules
for the unit tests.

Change-Id: I5c94484caadcb15daa34fbedda9774f215bb3cc7

doc/requirements.txt

@@ -0,0 +1,7 @@
+# The order of packages is significant, because pip processes them in the order
+# of appearance. Changing the order has an impact on the overall integration
+# process, which may cause wedges in the gate later.
+openstackdocstheme>=1.18.1 # Apache-2.0
+reno>=2.5.0 # Apache-2.0
+sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2;python_version>='3.4'  # BSD

test-requirements.txt

@@ -5,9 +5,6 @@
 hacking<0.11,>=0.10.0
 
 coverage>=3.6
-docutils>=0.11,!=0.13.1  # OSI-Approved Open Source, Public Domain
 discover
-sphinx>=1.6.2 # BSD
 oslotest>=1.2.0  # Apache-2.0
-openstackdocstheme>=1.17.0 # Apache-2.0
 fixtures

tox.ini

@@ -33,7 +33,14 @@ commands = python setup.py test --coverage --testr-args='{posargs}'
 
 [testenv:docs]
 basepython = python3
-commands = python setup.py build_sphinx
+deps =
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -r{toxinidir}/requirements.txt
+  -r{toxinidir}/doc/requirements.txt
+commands =
+  rm -rf doc/build
+  sphinx-build -W -b html doc/source doc/build/html
+whitelist_externals = rm
 
 [testenv:debug]
 basepython = python3