Update docs building

We need to move to new docs buidling structure as
per the Project Testing Interface (PTI) [0] for doc
build in OpenStack-Infra. More details [1].

[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: I699095c2eb2c818354fe0502cbbbadd3b9ef2656
diff --git a/tox.ini b/tox.ini
index d5e3b91..6445c64 100644
--- a/tox.ini
+++ b/tox.ini
@@ -46,11 +46,24 @@
                       rm
 
 [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 =
+  rm -rf doc/build
+  sphinx-build -W -b html doc/source doc/build/html
+whitelist_externals = rm
 
 [testenv:releasenotes]
+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 =
+  rm -rf releasenotes/build
   sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
+whitelist_externals = rm
 
 [testenv:debug]
 commands = oslo_debug_helper -t patrole_tempest_plugin/tests {posargs}