def label_exists(repo, label):
    """
    checks if a label exists in a repository's issue system
    :param repo: github.Repository - must be authenticated
    :param label: the label name to check
    :return: True if the label exists, False otherwise
    """
    labels = repo.get_labels()
    for l in labels:
        if label == l.name:
            return True
    return False