Fixed #8653: make formtools' security hash more rubust. Silly that I didn't...

        order, pickles the result with the SECRET_KEY setting, then takes an md5

        hash of that.

        """

        # Ensure that the hash does not change when a BooleanField's bound

        # data is a string `False' or a boolean False.

        # Rather than re-coding this special behaviour here, we

        # create a dummy BooleanField and call its clean method to get a

        # boolean True or False verdict that is consistent with

        # BooleanField.clean()

        dummy_bool = BooleanField(required=False)

        def _cleaned_data(bf):

            if isinstance(bf.field, BooleanField):

                return dummy_bool.clean(bf.data)

            return bf.data

        data = [(bf.name, _cleaned_data(bf) or '') for bf in form]

        data = [(bf.name, bf.field.clean(bf.data) or '') for bf in form]

        data.extend(args)

        data.append(settings.SECRET_KEY)