title: QuerySet object has no attribute 'user' on Django Rest Framework
body: <p>I cannot serialize a model to get results while performing requests on Django Rest Framework.</p>
  <h3>models.py</h3>
  <pre><code>class Karfarma(models.Model):
      user = models.OneToOneField(User, related_name='karfarma', on_delete=models.CASCADE)
      mobile = models.TextField(max_length=11)
      validation_number = models.TextField(max_length=5, blank=True, default=None)
      phone_number = models.TextField(max_length=10, blank=True, default=None)
      datetime_join_persian = models.DateTimeField(default=None, null=True)
  
      def __unicode__(self):
          return &quot;%s %s&quot; % (self.user.first_name, self.user.last_name)
  </code></pre>
  <h3>serializers.py</h3>
  <pre><code>class UserSerializer(serializers.ModelSerializer):
  
      class Meta:
          model = User
          fields = '__all__'
  </code></pre>
  <h3>views.py</h3>
  <pre><code>class UserList(APIView):
      queryset = User.objects.all()
  
      def get(self, request):
          users = User.objects.all()
          serializer = UserSerializer(users)
          return Response(serializer.data)
  </code></pre>
  <p>Here's the reduced version of the error which I get when I perform the request:</p>
  <blockquote>
  <p>AttributeError: Got AttributeError when attempting to get a value for field <code>user</code> on serializer <code>UserSerializer</code>.
  The serializer field might be named incorrectly and not match any attribute or key on the <code>QuerySet</code> instance.
  Original exception text was: 'QuerySet' object has no attribute 'user'.</p>
  </blockquote>