REMEMBER_COOKIE_DURATION must be a datetime.timedelta, instead got: (param0)

Raise code

isinstance(duration, int):
            duration = timedelta(seconds=duration)

        try:
            expires = datetime.utcnow() + duration
        except TypeError:
            raise Exception('REMEMBER_COOKIE_DURATION must be a ' +
                            'datetime.timedelta, instead got: {0}'.format(
                                duration))

        # actually set it
        response.set_cookie(cookie_name,
                            value=data,
                            expires=expires,