import zipfile


def read_diff_log(archivepath):
    """
    Read the diff-log.csv from a given archive file.

    :param archivepath: The path to the zip-archive
    :type archivepath: str
    :return: The diff-log.csv contents in ascii string form.
    :rtype: str
    """
    arch = zipfile.ZipFile(archivepath, mode='r')
    diff_log_file = arch.open("diff-log.csv")
    diff_log_bin = diff_log_file.read()
    diff_log = diff_log_bin.decode()
    diff_log_file.close()
    arch.close()
    return diff_log