docs: private static InputStream openSystemFile(String filename) throws FileNotFoundException {
      try {
        return new FileInputStream(filename);
      }
      catch(FileNotFoundException e) {
        // try with classloader
        String resname = File.separatorChar != '/' ? filename.replace(File.separatorChar, '/') : filename;
        ClassLoader cl = LoggingConfiguration.class.getClassLoader();
        InputStream result = cl.getResourceAsStream(resname);
        if(result != null) {
          return result;
        }
        // Sometimes, URLClassLoader does not work right. Try harder:
        URL u = cl.getResource(resname);
        if(u == null) {
          throw e;
        }
        try {
          URLConnection conn = u.openConnection();
          conn.setUseCaches(false);
          result = conn.getInputStream();
          if(result != null) {
            return result;
          }
        }
        catch(IOException x) {
          throw e; // Throw original error instead.
        }
        throw e;
      }
    }