Remove token from the store.

    :param opts: Salt master config options
    :param tok: Token to remove
    :returns: Empty dict if successful. None if failed.

def rm_token(opts, tok):
    '''
    Remove token from the store.

    :param opts: Salt master config options
    :param tok: Token to remove
    :returns: Empty dict if successful. None if failed.
    '''
    t_path = os.path.join(opts['token_dir'], tok)
    try:
        os.remove(t_path)
        return {}
    except (IOError, OSError):
        log.warning('Could not remove token %s', tok)