tox: Keeping going with docs and cleanup setup.cfg

1. Sphinx 1.8 introduced [1] the '--keep-going' argument which, as its name
suggests, keeps the build running when it encounters non-fatal errors.
This is exceptionally useful in avoiding a continuous edit-build loop
when undertaking large doc reworks where multiple errors may be
introduced.

2. pbr hasn't need the hook configuration since forever [2]

[1] https://github.com/sphinx-doc/sphinx/commit/e3483e9b045
[2] c84876dc0f

Change-Id: I421c88c7c5d2b494443986607e9ddfb87c02bc72

doc/requirements.txt

@@ -3,5 +3,5 @@
 # process, which may cause wedges in the gate later.
 
 openstackdocstheme>=1.18.1 # Apache-2.0
-sphinx!=1.6.6,!=1.6.7,>=1.6.5,<2.0.0;python_version=='2.7' # BSD
-sphinx!=1.6.6,!=1.6.7,>=1.6.5;python_version>='3.4' # BSD
+sphinx>=1.8.0,<2.0.0;python_version=='2.7' # BSD
+sphinx>=1.8.0,!=2.1.0;python_version>='3.4' # BSD

setup.cfg

@@ -24,10 +24,6 @@ classifier =
     Programming Language :: Python :: 3.7
     Topic :: Internet :: WWW/HTTP
 
-[global]
-setup-hooks =
-    pbr.hooks.setup_hook
-
 [files]
 packages =
     watcher_dashboard

tox.ini

@@ -41,7 +41,7 @@ commands = /bin/bash run_tests.sh -N --integration --selenium-headless {posargs}
 
 [testenv:releasenotes]
 basepython = python3
-commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
+commands = sphinx-build -a -E -W -d releasenotes/build/doctrees --keep-going -b html releasenotes/source releasenotes/build/html
 
 [testenv:cover]
 basepython = python3
@@ -64,7 +64,7 @@ whitelist_externals =
   make
 commands =
   rm -rf doc/build/pdf
-  sphinx-build -W -b latex doc/source doc/build/pdf
+  sphinx-build -W --keep-going -b latex doc/source doc/build/pdf
   make -C doc/build/pdf
 
 [testenv:debug]