def parse_commit_range(repo, committishs):
    """Parse a string referring to a range of commits.

    :param repo: A `Repo` object
    :param committishs: A string referring to a range of commits.
    :return: An iterator over `Commit` objects
    :raise KeyError: When the reference commits can not be found
    :raise ValueError: If the range can not be parsed
    """
    return iter([repo[committishs]])
