[docs] [issue30380] Sphinx 1.6.1 raising new warnings in docs build

[Serhiy Storchaka]

Changes by Serhiy Storchaka <storchaka+cpython at gmail.com>:


----------
pull_requests: +1704

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue30380>
_______________________________________