text: """
  AutoSlugField taken from django-extensions at
  15d3eb305957cee4768dd86e44df1bdad341a10e
  Uses Oscar's slugify function instead of Django's
  
  Copyright (c) 2007 Michael Trier
  
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
  
  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.
  
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  THE SOFTWARE.
  """
  
  import re
  
  from django.conf import settings
  from django.utils import six
  
  from oscar.core.utils import slugify
  
  from .slugfield import SlugField
  
  try:
      from django.utils.encoding import force_unicode  # NOQA
  except ImportError:
      from django.utils.encoding import force_text as force_unicode  # NOQA
  
  
  class AutoSlugField(SlugField):
      """ AutoSlugField
  
      By default, sets editable=False, blank=True.
  
      Required arguments:
  
      populate_from
          Specifies which field or list of fields the slug is populated from.
  
      Optional arguments:
  
      separator
          Defines the used separator (default: '-')
  
      overwrite
          If set to True, overwrites the slug on every save (default: False)
  
      Inspired by SmileyChris' Unique Slugify snippet:
      http://www.djangosnippets.org/snippets/690/
      """
      def __init__(self, *args, **kwargs):
          kwargs.setdefault('blank', True)
          kwargs.setdefault('editable', False)
  
          populate_from = kwargs.pop('populate_from', None)
          if populate_from is None:
              raise ValueError("missing 'populate_from' argument")
          else:
              self._populate_from = populate_from
              self._populate_from_org = populate_from
          self.separator = kwargs.pop('separator', six.u('-'))
          self.overwrite = kwargs.pop('overwrite', False)
          self.uppercase = kwargs.pop('uppercase', False)
          self.allow_duplicates = kwargs.pop('allow_duplicates', False)
  
          # not override parameter if it was passed explicitly,
          # so passed parameters takes precedence over the setting
          if settings.OSCAR_SLUG_ALLOW_UNICODE:
              kwargs.setdefault('allow_unicode', settings.OSCAR_SLUG_ALLOW_UNICODE)
  
          super(AutoSlugField, self).__init__(*args, **kwargs)
  
      def _slug_strip(self, value):
          """
          Cleans up a slug by removing slug separator characters that occur at
          the beginning or end of a slug.
  
          If an alternate separator is used, it will also replace any instances
          of the default '-' separator with the new separator.
          """
          re_sep = '(?:-|%s)' % re.escape(self.separator)
          value = re.sub('%s+' % re_sep, self.separator, value)
          return re.sub(r'^%s+|%s+$' % (re_sep, re_sep), '', value)
  
      def get_queryset(self, model_cls, slug_field):
          for field, model in model_cls._meta.get_fields_with_model():
              if model and field == slug_field:
                  return model._default_manager.all()
          return model_cls._default_manager.all()
  
      def slugify_func(self, content):
          if content:
              return slugify(content)
          return ''
  
      def create_slug(self, model_instance, add):  # NOQA (too complex)
          # get fields to populate from and slug field to set
          if not isinstance(self._populate_from, (list, tuple)):
              self._populate_from = (self._populate_from, )
          slug_field = model_instance._meta.get_field(self.attname)
  
          # only set slug if empty and first-time save, or when overwrite=True
          if add and not getattr(model_instance, self.attname) or self.overwrite:
              # slugify the original field content and set next step to 2
              def slug_for_field(field):
                  return self.slugify_func(getattr(model_instance, field))
              slug = self.separator.join(map(slug_for_field, self._populate_from))  # NOQA
              next = 2
          else:
              # get slug from the current model instance
              slug = getattr(model_instance, self.attname)
              # model_instance is being modified, and overwrite is False,
              # so instead of doing anything, just return the current slug
              return slug
  
          # strip slug depending on max_length attribute of the slug field
          # and clean-up
          slug_len = slug_field.max_length
          if slug_len:
              slug = slug[:slug_len]
          slug = self._slug_strip(slug)
  
          if self.uppercase:
              slug = slug.upper()
  
          original_slug = slug
  
          if self.allow_duplicates:
              return slug
  
          # exclude the current model instance from the queryset used in finding
          # the next valid slug
          queryset = self.get_queryset(model_instance.__class__, slug_field)
          if model_instance.pk:
              queryset = queryset.exclude(pk=model_instance.pk)
  
          # form a kwarg dict used to impliment any unique_together contraints
          kwargs = {}
          for params in model_instance._meta.unique_together:
              if self.attname in params:
                  for param in params:
                      kwargs[param] = getattr(model_instance, param, None)
          kwargs[self.attname] = slug
  
          # increases the number while searching for the next valid slug
          # depending on the given slug, clean-up
          while not slug or queryset.filter(**kwargs):
              slug = original_slug
              end = '%s%s' % (self.separator, next)
              end_len = len(end)
              if slug_len and len(slug) + end_len > slug_len:
                  slug = slug[:slug_len - end_len]
                  slug = self._slug_strip(slug)
              slug = '%s%s' % (slug, end)
              kwargs[self.attname] = slug
              next += 1
          return slug
  
      def pre_save(self, model_instance, add):
          value = force_unicode(self.create_slug(model_instance, add))
          setattr(model_instance, self.attname, value)
          return value
  
      def get_internal_type(self):
          return "SlugField"
  
      def deconstruct(self):
          name, path, args, kwargs = super(AutoSlugField, self).deconstruct()
          kwargs['populate_from'] = self._populate_from_org
          if not self.separator == six.u('-'):
              kwargs['separator'] = self.separator
          if self.overwrite is not False:
              kwargs['overwrite'] = True
          if self.allow_duplicates is not False:
              kwargs['allow_duplicates'] = True
          return name, path, args, kwargs
  