title: "ProgrammingError: column "genre_id" of relation "music_album" does not exist" while the column does exist
body: <p>I have the following models :</p>
  
  <pre><code>class CulturalDocument(CacheMixin, models.Model):
      ...
      uuid = UUIDField(unique=True)
  
  
  class Genre(CulturalDocument):
      name = models.CharField(max_length=32)
      ...
  
  class Album(CulturalDocument):
      ...
      genre = models.ForeignKey(Genre, null=True, blank=True)
  </code></pre>
  
  <p>I added the <code>genre</code> attribute with a south migration.</p>
  
  <p>I can see the column <code>genre_id</code> in the table <code>music_album</code> using pg_admin.</p>
  
  <p>However, when I do this :</p>
  
  <pre><code>    album = Album.objects.create(uuid=3,
                                   release_date=datetime(2000, 1, 1),
                                   title="Fantastic Album",
                                   right_holder=rh)
  </code></pre>
  
  <p>I get : </p>
  
  <pre><code> "ProgrammingError: column "genre_id" of relation "music_album" does not exist" while the column does exist
   LINE 1: ..._id", "title", "release_date", "right_holder_id", "genre_id"...
   .                                                            ^
  </code></pre>
  
  <p>Using PostGres 9.2 and Django 1.6 in Ubuntu 12.04.</p>
  
  <p>The generated SQL is :</p>
  
  <pre><code>INSERT INTO "music_album" ("culturaldocument_ptr_id", "title", "release_date", "right_holder_id", "genre_id") VALUES (%s, %s, %s, %s, %s)
  </code></pre>