title: Enum type django and rest framework
body: <p>I have a problem with the rest framework and one enum field. I get this error: </p>
  
  <pre><code>  File "/usr/local/lib/python2.7/dist-packages/coreapi/codecs/corejson.py", line 48, in decode_schema_from_corejson
      return schema_cls(title=title, description=description)
  TypeError: __init__() takes exactly 2 arguments (1 given)
  </code></pre>
  
  <p>when the model has this field:</p>
  
  <pre><code>class PuddleAtomStatus(ChoiceEnum):
      INVALID = "INVALID"
      OK = "OK"
  
  class PuddleAtom(Model):
      name = models.CharField(max_length=255, primary_key=True)
      ingestion_flow = models.CharField(max_length=256)
      status = EnumChoiceField(enm_class=PuddleAtomStaus) 
  </code></pre>
  
  <p>but anything is fine when </p>
  
  <pre><code>status = models.CharField(max_length=100)
  </code></pre>
  
  <p>I'm using  Django 1.11 and python 2.7 </p>
  
  <p>Is there a way to fix this and leave the model with the enum field ? </p>