@Override
    public String toString() {
        if (code == 0 && detailedMessage == null && cause == null) return message; // shortcut
        StringBuilder b = new StringBuilder();
        if (code != 0)
            b.append(code).append(": ");
        b.append(message);
        if (detailedMessage != null)
            b.append(": ").append(detailedMessage);
        if (cause != null)
            append(cause, b);
        return b.toString();
    }
Returns a formatted message containing the information in this
container-core/src/main/java/com/yahoo/processing/request/ErrorMessage.java