def slugify(value, allow_unicode=False):
    """
    Convert to ASCII if 'allow_unicode' is False. Convert spaces to hyphens.
    Remove characters that aren't alphanumerics, underscores, or hyphens.
    Convert to lowercase. Also strip leading and trailing whitespace.
    Copyright: https://docs.djangoproject.com/en/1.9/_modules/django/utils/text/#slugify
    TODO: replace after stopping support for Django 1.8
    """
    value = force_text(value)
    if allow_unicode:
        value = unicodedata.normalize('NFKC', value)
        value = re.sub('[^\w\s-]', '', value, flags=re.U).strip().lower()
        return mark_safe(re.sub('[-\s]+', '-', value, flags=re.U))
    value = unicodedata.normalize('NFKD', value).encode('ascii', 'ignore').decode('ascii')
    value = re.sub('[^\w\s-]', '', value).strip().lower()
    return mark_safe(re.sub('[-\s]+', '-', value))