docs: def chmod_add_executable(fpath, group=True, user=True):
      """
      References:
          http://stackoverflow.com/questions/15607903/python-module-os-chmodfile-664-does-not-change-the-permission-to-rw-rw-r-bu
          http://www.tutorialspoint.com/python/os_chmod.htm
          https://en.wikipedia.org/wiki/Chmod
      """
      import stat
      orig_mode = os.stat(fpath).st_mode
      new_mode = orig_mode
      if group:
          new_mode |= stat.S_IXGRP
      if user:
          # new_mode |= stat.S_IXUSR | stat.S_IEXEC
          new_mode |= stat.S_IXGRP | stat.S_IEXEC
      os.chmod(fpath, new_mode)