private static void printToStdErr(String s, Throwable throwable) {
        if (s != null) {
            System.err.println(s);
        }
        if (throwable != null) {
            StringWriter sw = new StringWriter();
            PrintWriter pw = new PrintWriter(sw);
            throwable.printStackTrace(pw);
            System.err.print(sw.toString());
            System.err.print("\n");
        }
    }
Returns the directory that log files exist in. The directory name will
have a File.separator as the last character in the string.

@return the directory that log files exist in.
xmppserver/src/main/java/org/jivesoftware/util/Log.java