docs: def deconstruct(self):
          """
          to support Django 1.7 migrations, see also the add_introspection_rules
          section at bottom of this file for South + earlier Django versions
          """
          name, path, args, kwargs = super(
              ExclusiveBooleanField, self).deconstruct()
          if self._on_fields:
              kwargs['on'] = self._on_fields
          return name, path, args, kwargs