title: (fields.E300) Field defines a relation with model which is either not installed, or is abstract
body: <p>I have 2 apps installed in my Django Project "aplikacja"</p>
  
  <p>The first one named: "Godzina"</p>
  
  <pre><code>from django.db import models
  
  class Godzina (models.Model):
          GODZINA = (
          ('19', '19'),
          ('20', '20'),
          ('21', '21'),
          )
          godzina = models.CharField(max_length=6, choices=GODZINA, verbose_name='jezyk')
  </code></pre>
  
  <p>and the second named: "UserProfile"</p>
  
  <pre><code>from django.db import models
  from django.contrib.auth.models import User
  from godzina.models import Godzina
  
  class UserProfile(models.Model):
      czas = models.ForeignKey('Godzina')   
      user = models.OneToOneField(User)
  </code></pre>
  
  <p>I'm getting such error:</p>
  
  <pre><code>userprofile.UserProfile.czas: (fields.E300) Field defines a relation with model 'Godzina', which is either not installed, or is abstract.
  </code></pre>
  
  <p>What does it mean? I would like that User can only pick such time as an administrator put in the app "Godzina" For example I'm defining hours 19 pm, 20 pm and then user can choose those values in UserProfile app</p>
  
  <p>Is it possible to fix this problem?</p>