def bool_on_off(process, longname, flag, value):
    """ Phrase Boolean values as 'on' or 'off' """
    if value in [True, 'on', 'On']:
        return "on"
    if value in [False, 'off', 'Off']:
        return "off"
    # Anything else wasn't a bool!
    raise ValueError("Flag value '%s' wasn't boolean." % repr(value))