In the diff file, you are assuming that python 3.5 is intalled and QET is executing on linx. If you want I try to fix, but maybe is easy a menu command that launch the qet_tb_generator if it's installed.
If it's not intalled, migth appears a msg indicating how to do, and a link to https://pypi.python.org/pypi/qet-tb-generator/
In next versions of QET, the menu entry remain, but it will launch the internal borne generator instead of qet_tb_generator.