docs: def packtar(tarfile, files, srcdir):
      """ Pack the given files into a tar, setting cwd = srcdir"""
      nullfd = open(os.devnull, "w")
      tarfile = cygpath(os.path.abspath(tarfile))
      log.debug("pack tar %s from folder  %s with files ", tarfile, srcdir)
      log.debug(files)
      try:
          check_call([TAR, '-czf', tarfile] + files, cwd=srcdir,
                     stdout=nullfd, preexec_fn=_noumask)
      except Exception:
          log.exception("Error packing tar file %s to %s", tarfile, srcdir)
          raise
      nullfd.close()