import importlib


class ModelPermsAppConfigMixin:
    @property
    def permission_groups(self):
        try:
            permissions = importlib.import_module('.groups', self.name)
            return getattr(permissions, 'permission_groups')
        except (ModuleNotFoundError, AttributeError):
            raise PermissionsNotDefined


class PermissionsNotDefined(Exception):
    pass