Use -W and make docs to build without warnings

Author: humitos

docs/conf.py

@@ -128,7 +128,7 @@
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['_static']
+# html_static_path = ['_static']
 
 # Custom sidebar templates, must be a dictionary that maps document names
 # to template names.

tox.ini

@@ -31,4 +31,4 @@ setenv =
   READTHEDOCS_PROJECT = sphinx-hoverxref
   READTHEDOCS_VERSION = latest
 commands =
-    sphinx-build -E -q -b html -d {envtmpdir}/doctrees . {envtmpdir}/html
+    sphinx-build -W -E -q -b html -d {envtmpdir}/doctrees . {envtmpdir}/html