fixed Python 3 issue in sphinxtogithub.py

Without those parentheses `make doc` will fail with Python 3

Signed-off-by: Paul Weingardt <weingardt.dev@gmail.com>
Merge pull request #353 from pweingardt/master

fixed Python 3 issue in sphinxtogithub.py

Signed-off-by: David Aguilar <davvid@gmail.com>