You are referencing the
PushedWalkBtn function before you define it. That is why the error says
PushedWalkBtn is not defined.
Just place the function definition above the action definition and it should work:
Code:
def PushedWalkBtn():
stopcollide()
carPAUSEaction()
inviscar()
action = vizact.sequence(vizact.call(Pushed.visible,True),vizact.call(PushedWalkBtn))
vizact.onpick( PushBox, Pushed.runAction, action)