old_contents: from django.core.urlresolvers import reverse
  from django.db import models
  from django.utils import timezone
  
  from core.models import TimeStampedModel, BaseModel, AuthorModel, PublicModel, ImageModel, CommentModel
  from core.util import unique_boolean
  
  from .managers import PostManager, ImageManager
  import util
  
  
  STATUS_CHOICES = [('d', 'Draft'),  ('p', 'Published'), ('w', 'Withdrawn')]
  
  
  class Post(TimeStampedModel, BaseModel, AuthorModel, PublicModel, CommentModel):
  
      pubdate = models.DateTimeField('publication date', default=timezone.now())
      status = models.CharField(max_length=1, choices=STATUS_CHOICES)
      body = models.TextField()
  
      objects = PostManager()
  
      def get_absolute_url(self):
          return reverse('post_detail', kwargs={'id': self.id, 'slug': self.slug})
  
      @property
      def thumbnail(self):
          thumbnail = self.image_set.filter(status=True).filter(thumbnail=True)
          # 'thumbnail' field is unique
          return thumbnail.get() if thumbnail else None
  
      class Meta:
          ordering = ['-pubdate']
  
  
  # Keep the 'thumbnail' field unique for the images of each post
  @unique_boolean('thumbnail', subset=['post'])
  class Image(TimeStampedModel, BaseModel, ImageModel):
  
      image = models.ImageField(upload_to=util.get_image_path)
  
      post = models.ForeignKey(Post)
      objects = ImageManager()
  
      class Meta:
          ordering = ['-post__pubdate', '-created']
  
new_contents: from django.core.urlresolvers import reverse
  from django.db import models
  from django.utils import timezone
  
  from core.models import TimeStampedModel, BaseModel, AuthorModel, PublicModel, ImageModel, CommentModel
  from core.utils import unique_boolean
  
  from .managers import PostManager, ImageManager
  import util
  
  
  STATUS_CHOICES = [('d', 'Draft'),  ('p', 'Published'), ('w', 'Withdrawn')]
  
  
  class Post(TimeStampedModel, BaseModel, AuthorModel, PublicModel, CommentModel):
  
      pubdate = models.DateTimeField('publication date', default=timezone.now())
      status = models.CharField(max_length=1, choices=STATUS_CHOICES)
      body = models.TextField()
  
      objects = PostManager()
  
      def get_absolute_url(self):
          return reverse('post_detail', kwargs={'id': self.id, 'slug': self.slug})
  
      @property
      def thumbnail(self):
          thumbnail = self.image_set.filter(status=True).filter(thumbnail=True)
          # 'thumbnail' field is unique
          return thumbnail.get() if thumbnail else None
  
      class Meta:
          ordering = ['-pubdate']
  
  
  # Keep the 'thumbnail' field unique for the images of each post
  @unique_boolean('thumbnail', subset=['post'])
  class Image(TimeStampedModel, BaseModel, ImageModel):
  
      image = models.ImageField(upload_to=util.get_image_path)
  
      post = models.ForeignKey(Post)
      objects = ImageManager()
  
      class Meta:
          ordering = ['-post__pubdate', '-created']
  
subject: Fix import error