Cleanup docs building

This repo is now testing only with Python 3, so let's make
a few cleanups:
- Remove obsolete sections from setup.cfg
- Switch to using sphinx-build
- Remove install_command from tox.ini, the default is fine
- cleanup tox.ini
- Update pbr requirement

Change-Id: I0adc74190fa820434a46b2a6bf9247ca6eb3e51d

requirements.txt

@@ -1,4 +1,4 @@
-pbr>=0.6,!=0.7,<1.0
+pbr!=2.1.0,>=2.0.0 # Apache-2.0
 sphinx>=2.0.0,!=2.1.0 # BSD
 openstackdocstheme>=2.2.1 # Apache-2.0
 yasfb>=0.5.1

setup.cfg

@@ -11,15 +11,3 @@ classifier =
     Intended Audience :: Developers
     License :: OSI Approved :: Apache Software License
     Operating System :: POSIX :: Linux
-
-[build_sphinx]
-source-dir = doc/source
-build-dir = doc/build
-all-files = True
-warning-is-error = True
-
-[pbr]
-warnerrors = True
-
-[upload_sphinx]
-upload-dir = doc/build/html

tox.ini

@@ -5,19 +5,17 @@ skipsdist = True
 
 [testenv]
 usedevelop = True
-install_command = pip install -U {opts} {packages}
+basepython = python3
 setenv =
    VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 
 [testenv:venv]
-basepython = python3
 commands = {posargs}
 
 [testenv:docs]
-basepython = python3
-commands = python setup.py build_sphinx
+commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:spelling]
 deps =