Create doc/requirements.txt

This change migrates the docs building requirements as outlined in
the Project Testing Interface[0]. One benefit of this that we no longer
load all the doc-generating modules when we run tox unittest. See [1] for
more details.

[0] https://governance.openstack.org/tc/reference/project-testing-interface.html#documentation
[1] http://lists.openstack.org/pipermail/openstack-dev/2017-November/124815.html

Change-Id: If5ac500e9e0fc99e75b98f3d55858dfc56dee6ff
Signed-off-by: Tin Lam <tin@irrational.io>

doc/requirements.txt

@@ -0,0 +1,6 @@
+# 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.
+sphinx>=1.6.2 # BSD
+sphinx_rtd_theme==0.2.4
+reno>=2.5.0 # Apache-2.0

test-requirements.txt

@@ -14,11 +14,8 @@ os-testr>=0.8.0 # Apache-2.0
 testrepository>=0.0.18 # Apache-2.0/BSD
 testtools>=1.4.0 # MIT
 bandit>=1.1.0 # Apache-2.0
-sphinx>=1.6.2 # BSD
 gabbi==1.35.1
-sphinx_rtd_theme==0.2.4
 pifpaf==0.10.0
-reno>=2.5.0 # Apache-2.0
 pytest-html==1.16.0
 
 # NOTE(fmontei): The requirement below is only included because readthedocs

tox.ini

@@ -64,6 +64,7 @@ commands =
     bandit -r deckhand -x deckhand/tests -n 5
 
 [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
 
 [testenv:genconfig]
@@ -87,6 +88,7 @@ ignore = E127,E128,E129,E131,H405
 exclude =  .venv,.git,.tox,dist,*lib/python*,*egg,build,releasenotes,doc
 
 [testenv:docs]
+deps = -r{toxinidir}/doc/requirements.txt
 commands =
     rm -rf doc/build
     python setup.py build_sphinx {posargs}