Switch to sphinx-build and cleanup

Switch to using modern sphinx-build.
Remove obsolete install_command from tox.ini.
Remove cruft from setup.cfg.

Change-Id: I0f3e9d980c25545a0085d406bf4f45fc6d6f4fbd

setup.cfg

@@ -6,6 +6,7 @@ description-file =
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/sphinx-feature-classification/latest/
+python-requires = >=3.6
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -16,23 +17,13 @@ classifier =
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3 :: Only
+    Programming Language :: Python :: Implementation :: CPython
 
 [files]
 packages =
     sphinx_feature_classification
 
-[wheel]
-universal = 1
-
-[build_sphinx]
-all-files = 1
-warning-is-error = 1
-source-dir = doc/source
-build-dir = doc/build
-
-[upload_sphinx]
-upload-dir = doc/build/html
-
 [compile_catalog]
 directory = sphinx_feature_classification/locale
 domain = sphinx_feature_classification

tox.ini

@@ -10,7 +10,6 @@ ignore_basepython_conflict = True
 [testenv]
 basepython = python3
 usedevelop = True
-install_command = pip install {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
    PYTHONWARNINGS=default::DeprecationWarning
@@ -29,7 +28,8 @@ commands = {posargs}
 commands = python setup.py test --coverage --testr-args='{posargs}'
 
 [testenv:docs]
-commands = python setup.py build_sphinx
+commands =
+  sphinx-build -W --keep-going -b html -d doc/build/doctrees doc/source doc/build/html
 
 [testenv:releasenotes]
 commands =