AttributeError while raising Exception "TransitionCannotStart"

[brot]

If you are using another name than state for your StateField, the TransitionCannotStart Exception raises AttributeError, because instance.state is not defined

https://github.com/vikingco/django-states2/blob/master/django_states/exceptions.py#L46

class TransitionCannotStart(TransitionException):
    def __init__(self, instance, transition):
        TransitionException.__init__(self, "Transition '%s' on %s cannot start in the state '%s'" %
                    (transition, instance.__class__.__name__, instance.state))