tox: Keeping going with docs

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.

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

Change-Id: Ib1749e690c22663955985f0c3b718ed6223be223

doc/requirements.txt

@@ -3,6 +3,6 @@
 # process, which may cause wedges in the gate later.
 openstackdocstheme>=1.20.0 # Apache-2.0
 reno>=2.5.0 # 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
 sphinxcontrib-apidoc>=0.2.0  # BSD

lower-constraints.txt

@@ -6,5 +6,5 @@ oslo.i18n==3.15.3
 openstackdocstheme==1.20.0
 oslotest==3.2.0
 reno==2.5.0
-Sphinx==1.6.5
+Sphinx==1.8.0
 stestr==1.0.0

tox.ini

@@ -31,7 +31,10 @@ deps =
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/doc/requirements.txt
 basepython = python3
-commands = sphinx-build -W -b html doc/source doc/build/html
+whitelist_externals = rm
+commands =
+  rm -fr doc/build
+  sphinx-build -W --keep-going -b html doc/source doc/build/html
 
 [testenv:cover]
 basepython = python3
@@ -39,9 +42,12 @@ commands = python setup.py test --coverage --coverage-package-name=oslo_limit --
 
 [testenv:releasenotes]
 basepython = python3
+whitelist_externals = rm
 deps =
   -r{toxinidir}/doc/requirements.txt
-commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
+commands =
+  rm -rf releasenotes/build
+  sphinx-build -a -E -W -d releasenotes/build/doctrees --keep-going -b html releasenotes/source releasenotes/build/html
 
 [flake8]
 show-source = True