List enrolled courses.

    @param args: Command-line arguments.
    @type args: namedtuple

def list_courses(args):
    """
    List enrolled courses.

    @param args: Command-line arguments.
    @type args: namedtuple
    """
    session = get_session()
    login(session, args.username, args.password)
    extractor = CourseraExtractor(session)
    courses = extractor.list_courses()
    logging.info('Found %d courses', len(courses))
    for course in courses:
        logging.info(course)