title: Escpaing issue with 'Not a valid choice' in Django Rest Framework
body: <p>I have a model with a status field that looks something like this:</p>
  <pre><code>PENDING = 'pending'
  DONE = 'done'
  CANCELED = 'canceled'
  
  class Event:
      EVENT_STATUSES = [(1, PENDING), (2, DONE), (3, CANCELED)]
      status = models.CharField(max_length=20, choices=EVENT_STATUSES, default=PENDING)
  </code></pre>
  <p>I have a serializer:</p>
  <pre><code>class EventUpdateSerializer(serializers.ModelSerializer):
  
      class Meta:
          model = Event
          fields = ('status')
  </code></pre>
  <p>And when it is called with the following JSON:</p>
  <pre><code>{
      &quot;status&quot;: &quot;done&quot;
  }
  </code></pre>
  <p>I get the response:</p>
  <pre><code>{
    &quot;status&quot;: [
      &quot;\&quot;done\&quot; is not a valid choice.&quot;
    ]
  }
  </code></pre>
  <p>I think the problem is the escaping of done, but why? And how do I prevent it?</p>
  <p>(I have a content-type application/json header).</p>