Add support for new doc PTI jobs

Implement optional cleanup to support the new PTI jobs for
documentation which won't use tox anymore.

Docs tox environment will still available for developers
but it is no loger used in the gate to construct the documentation.

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

Change-Id: I411115977f095e0e0ee01b65d01fe8c389a8754e

doc/requirements.txt

@@ -0,0 +1,2 @@
+sphinx>=1.2.1,!=1.3b1,<1.4 # BSD
+oslosphinx>=4.7.0 # Apache-2.0

test-requirements.txt

@@ -6,8 +6,6 @@ hacking>=0.12.0,<0.13 # Apache-2.0
 
 coverage>=4.0 # Apache-2.0
 python-subunit>=0.0.18 # Apache-2.0/BSD
-sphinx>=1.2.1,!=1.3b1,<1.4 # BSD
-oslosphinx>=4.7.0 # Apache-2.0
 oslotest>=1.10.0 # Apache-2.0
 testrepository>=0.0.18  # Apache-2.0/BSD
 testscenarios>=0.4  # Apache-2.0/BSD

tox.ini

@@ -37,7 +37,8 @@ commands =
     coverage report
 
 [testenv:docs]
-commands = python setup.py build_sphinx
+deps = -r{toxinidir}/doc/requirements.txt
+commands = sphinx-build -b html doc/source doc/build/html
 
 [testenv:releasenotes]
 commands =