Put on a pair of parens (with no catch tag) outside the regex,
    if the regex is not yet packed;
    modified the outmost parens by adding nocatch tag

def nocatch(regex):
    """
    Put on a pair of parens (with no catch tag) outside the regex,
    if the regex is not yet packed;
    modified the outmost parens by adding nocatch tag
    """
    if is_solid(regex) and not is_packed(regex):
        return regex
    else:
        return '(?:{})'.format(danger_unpack(regex))