Moved BooleanField 'required' validation in validate()

            value = False

        else:

            value = bool(value)

        value = super(BooleanField, self).to_python(value)

        return super(BooleanField, self).to_python(value)

    def validate(self, value):

        if not value and self.required:

            raise ValidationError(self.error_messages['required'])

        return value

    def _has_changed(self, initial, data):

        # Sometimes data or initial could be None or '' which should be the