Add doc/requirements

We need to specify doc requirements in doc/requirements.txt
to avoid problems with the pip resolver [1] for the release team [2][3].

Removing specific doc requirements from test-requirements.txt.

The problem here is that this repos haven't doc/requirements.txt file
and by default in this case zuul will use the test-requirements.txt file
to pull requirements [4].

This requirements file contains extra requirements like flake8 that
collided with those allowed in our job environment and so the new pip
resolver fails to install these requirements and the job exits in error.

This project meet the conditions leading to the bug.

[1] http://lists.openstack.org/pipermail/release-job-failures/2021-January/001500.html
[2] http://lists.openstack.org/pipermail/openstack-discuss/2021-January/019611.html
[3] http://lists.openstack.org/pipermail/openstack-discuss/2021-January/019612.html
[4] https://opendev.org/zuul/zuul-jobs/src/branch/master/roles/ensure-sphinx/tasks/main.yaml#L36

Change-Id: I582c7b1b8008e72f376a24a58ca1ee5ac4d933bb

doc/requirements.txt

@@ -0,0 +1,5 @@
+# documentation
+sphinx>=2.0.0,!=2.1.0 # BSD
+os-api-ref>=1.4.0 # Apache-2.0
+reno>=3.1.0 # Apache-2.0
+openstackdocstheme>=2.2.1 # Apache-2.0

test-requirements.txt

@@ -22,9 +22,4 @@ testscenarios>=0.4 # Apache-2.0/BSD
 testtools>=2.2.0 # MIT
 tempest>=17.1.0 # Apache-2.0
 
-# documentation
 doc8>=0.6.0 # Apache-2.0
-sphinx>=2.0.0,!=2.1.0 # BSD
-os-api-ref>=1.4.0 # Apache-2.0
-reno>=3.1.0 # Apache-2.0
-openstackdocstheme>=2.2.1 # Apache-2.0

tox.ini

@@ -65,6 +65,8 @@ commands =
   {[testenv:checkniceness]commands}
 
 [testenv:docs]
+deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+       -r{toxinidir}/doc/requirements.txt
 description = Builds api-ref, api-guide, releasenotes and devdocs
 commands =
   {[testenv:devdocs]commands}
@@ -72,6 +74,7 @@ commands =
   {[testenv:releasenotes]commands}
 
 [testenv:pdf-docs]
+deps = {[testenv:docs]deps}
 envdir = {toxworkdir}/docs
 whitelist_externals =
   make
@@ -82,6 +85,7 @@ commands =
   make -C doc/build/pdf
 
 [testenv:api-ref]
+deps = {[testenv:docs]deps}
 description = Called from CI scripts to test and publish the API Ref
 commands =
   rm -rf api-ref/build
@@ -90,6 +94,7 @@ commands =
     api-ref/source api-ref/build/html
 
 [testenv:releasenotes]
+deps = {[testenv:docs]deps}
 description = Called from CI script to test and publish the Release Notes
 commands =
   rm -rf releasenotes/build
@@ -97,6 +102,7 @@ commands =
     releasenotes/source releasenotes/build/html
 
 [testenv:devdocs]
+deps = {[testenv:docs]deps}
 description = Builds developer documentation
 commands =
   rm -rf doc/build doc/source/contributor/api