How to use the impostor.backend.ImpostorException function in Impostor

try:
                admin, uuser = [uname.strip() for uname in username.split(self.separator)]
            except ValueError:
                raise ImpostorException(_('Regular login, moving to next auth backend'))

            # Check if admin exists, authenticates and is allowed to impersonate another user
            adm_obj = get_user_model().objects.get(Q(username=admin) | Q(email=admin))
            if self.is_user_allowed_to_impersonate(adm_obj) and adm_obj.check_password(password):

                # get the user we want to impersonate
                auth_user = get_user_model().objects.get(Q(username=uuser) | Q(email=uuser))

                # Superusers can only be impersonated by other superusers
                if auth_user.is_superuser and not adm_obj.is_superuser:
                    auth_user = None
                    raise ImpostorException(_('Superuser can only be impersonated by a superuser.'))

                # creates the impostor log entry
                log_entry = ImpostorLog.objects.create(
                    impostor=adm_obj, imposted_as=auth_user, impostor_ip=self.ip_address(request)
                )

                # save impostor_token into the session
                self.save_impostor_token_into_session(log_entry, request)

        except Exception as e:  # Nope. Do nothing and let other backends handle it.
            log.info(msg=str(e))
        return auth_user