def _repoowner_reponame(repo_str, username):
    """Returns a repo owner and repo name from a repo string (owner username(or org)/repo name)
    If only repo is given, username will be provided username who's using the API
    
    Arguments:
        repo_str str -- Full repo string (owner username(or org)/repo name)
        username str -- Username of current user
    
    Raises:
        ValueError -- Invalid repo_str
    """

    user = ""
    repo = ""
    split = repo_str.split("/")
    if len(split) == 1:
        user = username
        repo = split[0]
    elif len(split) == 2:
        user = split[0]
        repo = split[1]
    else:
        raise ValueError(
            "Repo %s is made of %s parts, only 1 and 2 part repo names are supported" % (repo, str(len(repo)))
        )

    return user, repo