Use pre-commit hook to run doc8

Also create a separate doc requirements to install only required
packages during doc build or doc build check.

Change-Id: Ic0377868fdc3057314ae1dec0a0db0b1cc0c0b7b

.pre-commit-config.yaml

@@ -23,6 +23,11 @@ repos:
     hooks:
       - id: hacking
         additional_dependencies: []
+  - repo: https://github.com/PyCQA/doc8
+    rev: v1.1.2
+    hooks:
+      - id: doc8
+        files: doc/source/.*\.rst$
   - repo: https://github.com/asottile/pyupgrade
     rev: v3.18.0
     hooks:

doc/requirements.txt

@@ -0,0 +1,4 @@
+sphinx>=2.0.0 # BSD
+openstackdocstheme>=2.2.1 # Apache-2.0
+reno>=3.1.0 # Apache-2.0
+fixtures>=3.0.0 # Apache-2.0/BSD

test-requirements.txt

@@ -1,11 +1,5 @@
 coverage>=4.0 # Apache-2.0
 python-subunit>=1.0.0 # Apache-2.0/BSD
-sphinx>=2.0.0 # BSD
-openstackdocstheme>=2.2.1 # Apache-2.0
 stestr>=2.0.0 # Apache-2.0
 testtools>=2.2.0 # MIT
 fixtures>=3.0.0 # Apache-2.0/BSD
-doc8>=0.8.1 # Apache-2.0
-reno>=3.1.0 # Apache-2.0
-
-pre-commit>=2.6.0 # MIT

tox.ini

@@ -18,10 +18,12 @@ commands =
 commands = oslo_debug_helper {posargs}
 
 [testenv:pep8]
+deps =
+    pre-commit>=2.6.0 # MIT
+    {[testenv:docs]deps}
 commands =
     pre-commit run -a
     sphinx-build -b doctest doc/source doc/build
-    doc8 --ignore-path "doc/source/history.rst" doc/source
 
 [testenv:venv]
 commands = {posargs}
@@ -36,6 +38,9 @@ commands =
     coverage xml -o cover/coverage.xml
 
 [testenv:docs]
+deps =
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -W --keep-going -b html -d doc/build/doctrees doc/source doc/build/html
 
 [flake8]
@@ -45,5 +50,6 @@ ignore = E123,E125
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build
 
 [testenv:releasenotes]
+deps = {[testenv:docs]deps}
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html