It might be the same problem we had on Reaver due to me adding some extra 3 more spaces on the pixiewps pin print line.
I think on line 3111 you have to change:
to:WPSpin=WPSpin[WPSpin.find("WPS pin")+9:WPSpin.find("\n")]
WPSpin=WPSpin[WPSpin.find("WPS pin")+12:WPSpin.find("\n")]