old_contents: from django import forms
  
  __all__ = ('RatingField',)
  
  class RatingField(forms.ChoiceField):
      pass
new_contents: # coding=utf-8
  from __future__ import unicode_literals
  
  from django import forms
  
  
  __all__ = ('RatingField',)
  
  
  class RatingField(forms.ChoiceField):
      pass
  
subject: Update forms.py