def split_key_value(item):
    """Split KEY=VALUE specifier or raise an ValueError exception.

    :param item: input KEY=VALUE string option.
    :type item: str

    :raises ValueError: if cannot split

    :return: pair of split key and value
    :rtype: str, str
    """
    try:
        key, value = item.split('=', 1)
    except ValueError:
        raise ValueError('Missing KEY=VALUE pair in option "{}"'.format(item))
    return key, value