Python3 is required in 5.6 by pyside-setup.
Task-number: QTAUTO-345
Change-Id: If11ca425fa08cce8a518710ded0a6ec58159343d
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
(cherry picked from commit a5f3f8ed48)
(cherry picked from commit a765838889)
(cherry picked from commit 1859f9b26c)