title: Django REST framework: nested relationship: non_field_errors
body: <p>In a Django-REST-framework project I tried to use the nested relationship and got a "non_field_errors" in the browsable API web view.</p>
  
  <p>The code is from this part of the documentation: <em><a href="http://www.django-rest-framework.org/api-guide/relations#nested-relationships">http://www.django-rest-framework.org/api-guide/relations#nested-relationships</a></em></p>
  
  <p><strong>models.py:</strong></p>
  
  <pre><code>from django.db import models
  
  class Album(models.Model):
      album_name = models.CharField(max_length=100)
      artist = models.CharField(max_length=100)
  
  class Track(models.Model):
      album = models.ForeignKey(Album, related_name='tracks')
      order = models.IntegerField()
      title = models.CharField(max_length=100)
      #duration = models.IntegerField()
  
      class Meta:
          unique_together = ('album', 'order')
          ordering = ('order',)
  
      def __unicode__(self):
          return '%d: %s' % (self.order, self.title)
  </code></pre>
  
  <p><strong>serializers.py:</strong></p>
  
  <pre><code>from rest_framework import serializers
  from myapp.models import Album, Track
  
  class TrackSerializer(serializers.ModelSerializer):
      class Meta:
          model = Track
          fields = ('order', 'title')
  
  class AlbumSerializer(serializers.ModelSerializer):
      tracks = TrackSerializer(many=True)
  
      class Meta:
          model = Album
          fields = ('album_name', 'artist', 'tracks')
  </code></pre>
  
  <p>ERROR (at ../albums):</p>
  
  <p>The Track input field is marked red with the error message: non_field_errors.</p>
  
  <p>Clicking the OPTIONS button reveals the actual&amp;correct data structure:</p>
  
  <p>Tracks nested with their appropriate propertie</p>
  
  <p>The raw data input of the browsable browser view shows:</p>
  
  <pre><code>{
      "album_name": "", 
      "artist": "", 
      "tracks": null
  }
  </code></pre>
  
  <p>Posting some valid raw-data actually works. But it'd be nicer if the web interface form would work as well. Especially since I'm wondering if there's something funny going on anyway.</p>
  
  <p>Thank you in advance!</p>