src/main/java/com/alipay/remoting/rpc/RpcResponseResolver.java
private static String detailErrMsg(String clientErrMsg, ResponseCommand responseCommand) {
        RpcResponseCommand resp = (RpcResponseCommand) responseCommand;
        if (StringUtils.isNotBlank(resp.getErrorMsg())) {
            return String.format("%s, ServerErrorMsg:%s", clientErrMsg, resp.getErrorMsg());
        } else {
            return String.format("%s, ServerErrorMsg:null", clientErrMsg);
        }
    }
private static String detailErrMsg(String clientErrMsg, ResponseCommand responseCommand) {
        RpcResponseCommand resp = (RpcResponseCommand) responseCommand;
        if (StringUtils.isNotBlank(resp.getErrorMsg())) {
            return String.format("%s, ServerErrorMsg:%s", clientErrMsg, resp.getErrorMsg());
        } else {
            return String.format("%s, ServerErrorMsg:null", clientErrMsg);
        }
    }
Detail your error msg with the error msg returned from response command