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)
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