Merge pull request #2799 from jku/silence-docs-build

tox: Silence docs build

Author: kairoaraujo

tox.ini

@@ -54,4 +54,4 @@ deps =
     -r{toxinidir}/requirements/docs.txt
 
 commands =
-    sphinx-build -b html docs docs/build/html -W
+    sphinx-build --fail-on-warning --quiet --builder html docs docs/build/html