private static String getMessage(Throwable t) {
            String message = t.getMessage();
            if (t.getCause() == null) {
                if (message == null) return toShortClassName(t);
                return message;
            } else {
                if (message == null) return null;
                if (message.equals(t.getCause().getClass().getName() + ": " + t.getCause().getMessage())) return null;
                return message;
            }
        }
Returns a useful message from *this* exception, or null if none
configgen/src/main/java/com/yahoo/config/codegen/MakeConfig.java