Returns True if the file has already been downloaded

def already_downloaded(track, title, filename):
    """
    Returns True if the file has already been downloaded
    """
    global arguments
    already_downloaded = False

    if os.path.isfile(filename):
        already_downloaded = True
    if arguments['--flac'] and can_convert(filename) \
                           and os.path.isfile(filename[:-4] + ".flac"):
        already_downloaded = True
    if arguments['--download-archive'] and in_download_archive(track):
        already_downloaded = True

    if arguments['--flac'] and can_convert(filename) and os.path.isfile(filename):
        already_downloaded = False

    if already_downloaded:
        if arguments['-c'] or arguments['--remove']:
            logger.info('Track "{0}" already downloaded.'.format(title))
            return True
        else:
            logger.error('Track "{0}" already exists!'.format(title))
            logger.error('Exiting... (run again with -c to continue)')
            sys.exit(0)
    return False