private void appendException(Throwable throwable, StringBuilder builder) {
        if (throwable == null)
            return;

        String escapedStackTrace = VespaFormat.escape(stackTrace(throwable));
        builder.append("\\n").append("exception=").append("\\n").append(escapedStackTrace);
    }
Un-escapes previously escaped string.
note: look at com.yahoo.config.StringNode.unescapeQuotedString()

@param s String that might need un-escaping
@return Returns un-escaped string
vespalog/src/main/java/com/yahoo/log/VespaFormatter.java