private int mapExceptionToHttpErrorCode(AbstractEngineException data) {
        int errorCode = 500;
        if (data instanceof NotAuthorizedException) {
            errorCode = 403;
        }
        return errorCode;
    }
@see javax.ws.rs.ext.ExceptionMapper#toResponse(java.lang.Throwable)
gateway/api/rest-impl/src/main/java/io/apiman/gateway/api/rest/impl/mappers/RestExceptionMapper.java