Sphinx with backported fix for handling container directive in text builder

The patched package fixes this Sphinx bug, which breaks Beaker's build:

https://bitbucket.org/birkenfeld/sphinx/issue/1018/

The Sphinx update is stuck in Fedora due to missing tarballs on PyPI:

https://bugzilla.redhat.com/show_bug.cgi?id=946892#c3
Merge "Sphinx with backported fix for handling container directive in text builder"