title: Django 'str' object has no attribute 'values' in rest_framework
body: <p>When I use rest_framework to implement the api </p>
  
  <p>models.py:</p>
  
  <pre><code>class Store(models.Model):
  
      name = models.CharField(max_length=20)
  
      notes = models.TextField(blank=True, default='')
  
      def __str__(self):
  
          return self.name
  </code></pre>
  
  <p>myapp/api.py:</p>
  
  <pre><code>class StoreSerializer(serializers.ModelSerializer):
  
      class Meta:
  
          model = Store
  
  class StoreViewSet(viewsets.ModelViewSet):
  
      queryset = Store.objects.all()
  
      serializer_class = StoreSerializer
  
      permission_classes = (permissions.IsAuthenticatedOrReadOnly,)
  </code></pre>
  
  <p>project/api.py</p>
  
  <pre><code>v1 = routers.DefaultRouter()
  v1.register('store',StoreViewSet)
  v1.register('stores/menu_item',MenuItemViewSet)
  </code></pre>
  
  <p>urls.py</p>
  
  <pre><code>    from .api import v1
  
      urlpatterns = [
  
      url(r'^api/v1/', include(v1.urls)),
  
      ]
  </code></pre>
  
  <p>I met the following traceback</p>
  
  <blockquote>
    <p>AssertionError at /api/v1/store/
    ("Creating a ModelSerializer without either the 'fields' attribute or the 'exclude' attribute has been deprecated since 3.3.0, and is now disallowed. Add an explicit fields = '<strong>all</strong>' to the StoreSerializer serializer.",)</p>
  </blockquote>
  
  <p>So I add the <code>fields = '__all__'</code> to fix this error</p>
  
  <pre><code>class StoreSerializer(serializers.ModelSerializer):
  
     fields = '__all__'
  
     class Meta:
         model = Store
  </code></pre>
  
  <p>But next I met this <a href="http://dpaste.com/0E54BZJ" rel="noreferrer">traceback</a></p>
  
  <p>Based on that traceback I don't know which part is missing.</p>