move doc requirements to doc/requirements.txt

The documentation jobs now look for requirements in
doc/requirements.txt and do not use tox for release notes. Move the
dependency list from setup.cfg to the new file and update tox.ini so
the developer experience is consistent with what the CI system does.

Change-Id: I739c9eba21d1b9a680d6b0e9cc6a4cbaca56e543
Signed-off-by: Doug Hellmann <doug@doughellmann.com>
(cherry picked from commit 3ffdb1f0ba)

doc/requirements.txt

@@ -0,0 +1,3 @@
+openstackdocstheme>=1.17.0 # Apache-2.0
+reno>=2.5.0 # Apache-2.0
+sphinx>=1.6.2 # BSD

test-requirements.txt

@@ -9,3 +9,5 @@ coverage!=4.4,>=4.0 # Apache-2.0
 testrepository>=0.0.18 # Apache-2.0/BSD
 openstackdocstheme>=1.16.0 # Apache-2.0
 reno!=2.3.1,>=1.8.0 # Apache-2.0
+# sphinx is needed for testing the sphinxext module
+sphinx>=1.6.2 # BSD

tox.ini

@@ -14,6 +14,9 @@ distribute = False
 commands = python setup.py testr --testr-args='{posargs}'
 
 [testenv:venv]
+deps =
+  -r{toxinidir}/test-requirements.txt
+  -r{toxinidir}/doc/requirements.txt
 commands = {posargs}
 
 [testenv:pep8]
@@ -22,6 +25,7 @@ ignore = E251
 commands = flake8 stevedore setup.py
 
 [testenv:docs]
+deps = -r{toxinidir}/doc/requirements.txt
 commands = python setup.py build_sphinx
 
 [flake8]
@@ -30,4 +34,5 @@ show-source = True
 exclude=.venv,.git,.tox,dist,*lib/python*,*egg,build
 
 [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