docs: def packmar(marfile, srcdir):
      """Create marfile from the contents of srcdir"""
      nullfd = open(os.devnull, "w")
      files = [f[len(srcdir) + 1:] for f in findfiles(srcdir)]
      marfile = cygpath(os.path.abspath(marfile))
      try:
          check_call(
              [MAR, '-c', marfile] + files, cwd=srcdir, preexec_fn=_noumask)
      except Exception:
          log.exception("Error packing mar file %s from %s", marfile, srcdir)
          raise
      nullfd.close()