private void append(Throwable t, StringBuilder b) {
        String lastMessage = null;
        String message;
        for (; t != null; t = t.getCause(), lastMessage = message) {
            message = getMessage(t);
            if (message == null) continue;
            if (lastMessage != null && lastMessage.equals(message)) continue;
            if (!b.isEmpty())
                b.append(": ");
            b.append(message);
        }
    }
Returns a formatted message containing the information in this
container-core/src/main/java/com/yahoo/processing/request/ErrorMessage.java