main/py-sphinx: backport patch to the stable branch
Package py-sphinx needs python module imagesize since version 1.4.x, but this dependency is missing in py-sphinx 1.4.1-r0. For example llvm uses sphinx to build documentation and thus llvm package fails to build.
This broken py-sphinx package is currently in the v4.4 branch, so the patch should be backported.
(from redmine: issue id 5688, created on 2016-06-07)