title: Key error with Django Rest Framework
body: <p>I am building a RESTful API with DjangoRestFrameowork and came across an error when trying to use <code>choices</code> in my model. When accessing the api endpoint, I get the error <code>KeyError at /jobs/  u'job_type'</code>. My model has </p>
  
  <pre><code>JOB_CHOICES = (
      ('p', 'Paint'),
      ('pw', 'Pressure Wash'),
      ('h', 'Hourly'),
  )
  
  class Job(models.Model):
      created = models.DateTimeField(auto_now_add=True)
      budget = models.IntegerField()
      job_type = models.CharField(choices=JOB_CHOICES,
                                  default='p',
                                  max_length=100)
  </code></pre>
  
  <p>and my serializer looks like this:</p>
  
  <pre><code>class JobSerializer(serializers.ModelSerializer):
  
      class Meta:
        model = Job
        fields = ('pk',
                'budget',
                'created',
                'job_type',)
  </code></pre>
  
  <p>I can't figure out where this is going wrong. They do something very similar to this in the Django-Rest-Framework tutorial and I can't figure out what is different about mine. Any help would be appreciated!</p>
  
  <p>This is the full error:</p>
  
  <pre><code>Environment:
  
  
  Request Method: GET
  Request URL: http://127.0.0.1:8000/jobs/
  
  Django Version: 1.7.1
  Python Version: 2.7.6
  Installed Applications:
  ('django.contrib.admin',
   'django.contrib.auth',
   'django.contrib.contenttypes',
   'django.contrib.sessions',
   'django.contrib.messages',
   'django.contrib.staticfiles',
   'main',
   'rest_framework',
   'corsheaders')
  Installed Middleware:
  ('django.contrib.sessions.middleware.SessionMiddleware',
   'django.middleware.common.CommonMiddleware',
   'django.middleware.csrf.CsrfViewMiddleware',
   'django.contrib.auth.middleware.AuthenticationMiddleware',
   'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
   'django.contrib.messages.middleware.MessageMiddleware',
   'django.middleware.clickjacking.XFrameOptionsMiddleware',
   'corsheaders.middleware.CorsMiddleware',
   'django.middleware.common.CommonMiddleware')
  
  
  Traceback:
  File "/Library/Python/2.7/site-packages/django/core/handlers/base.py" in get_response
    111.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/Library/Python/2.7/site-packages/django/views/decorators/csrf.py" in wrapped_view
    57.         return view_func(*args, **kwargs)
  File "/Library/Python/2.7/site-packages/django/views/generic/base.py" in view
    69.             return self.dispatch(request, *args, **kwargs)
  File "/Library/Python/2.7/site-packages/rest_framework/views.py" in dispatch
    452.             response = self.handle_exception(exc)
  File "/Library/Python/2.7/site-packages/rest_framework/views.py" in dispatch
    449.             response = handler(request, *args, **kwargs)
  File "/Library/Python/2.7/site-packages/rest_framework/generics.py" in get
    241.         return self.list(request, *args, **kwargs)
  File "/Library/Python/2.7/site-packages/rest_framework/mixins.py" in list
    47.         return Response(serializer.data)
  File "/Library/Python/2.7/site-packages/rest_framework/serializers.py" in data
    618.         ret = super(ListSerializer, self).data
  File "/Library/Python/2.7/site-packages/rest_framework/serializers.py" in data
    213.                 self._data = self.to_representation(self.instance)
  File "/Library/Python/2.7/site-packages/rest_framework/serializers.py" in to_representation
    568.             self.child.to_representation(item) for item in iterable
  File "/Library/Python/2.7/site-packages/rest_framework/serializers.py" in to_representation
    435.                 ret[field.field_name] = field.to_representation(attribute)
  File "/Library/Python/2.7/site-packages/rest_framework/fields.py" in to_representation
    1041.         return self.choice_strings_to_values[six.text_type(value)]
  
  Exception Type: KeyError at /jobs/
  Exception Value: u'job_type'
  </code></pre>