def _normalize_percent_rgb(value):
    """
    Internal normalization function for clipping percent values into
    the permitted range (0%-100%, inclusive).

    """
    percent = value.split(u'%')[0]
    percent = float(percent) if u'.' in percent else int(percent)

    return u'0%' if percent < 0 \
        else u'100%' if percent > 100 \
        else u'{}%'.format(percent)