def repocsv(string):
    """
    >>> repocsv('org1/repo1, org2/repo2,org3/repo3 ,org4/repo4')
    ['org1/repo1', 'org2/repo2', 'org3/repo3', 'org4/repo4']
    """
    try:
        repos = [r.strip() for r in string.split(',')]
        return set(repos)
    except Exception as exc:
        raise argparse.ArgumentTypeError(exc.message)