def exec_from_dir(dirname=None, scent="scent.py"):
    """Runs the scent.py file from the given directory (cwd if None given).

    Returns module if loaded a scent, None otherwise.
    """
    if dirname is None:
        dirname = os.getcwd()
    files = os.listdir(dirname)

    if scent not in files:
        return None

    return load_file(os.path.join(dirname, scent))