'Returns a compiled regular expression, depending upon the activated
language-code.'

@property
def regex(self):

    language_code = get_language()
    if (language_code not in self._regex_dict):
        if isinstance(self._regex, six.string_types):
            regex = self._regex
        else:
            regex = force_text(self._regex)
        try:
            compiled_regex = re.compile(regex, re.UNICODE)
        except re.error as e:
            raise ImproperlyConfigured((u'"%s"    is    not    a    valid    regular    expression:    %s' % (regex, six.text_type(e))))
        self._regex_dict[language_code] = compiled_regex
    return self._regex_dict[language_code]
