old_contents: from django.core.exceptions import ValidationError
  from django.db import models
  from django.utils import simplejson
  
  
  class JSONField(models.TextField):
      """Simple JSON field that stores python structures as JSON strings
      on database.
      """
  
      __metaclass__ = models.SubfieldBase
  
      def to_python(self, value):
          """
          Convert the input JSON value into python structures, raises
          django.core.exceptions.ValidationError if the data can't be converted.
          """
          if self.blank and not value:
              return None
          if isinstance(value, basestring):
              try:
                  return simplejson.loads(value)
              except Exception, e:
                  raise ValidationError(str(e))
          else:
              return value
  
      def validate(self, value, model_instance):
          """Check value is a valid JSON string, raise ValidationError on
          error."""
          super(JSONField, self).validate(value, model_instance)
          try:
              return simplejson.loads(value)
          except Exception, e:
              raise ValidationError(str(e))
  
      def get_db_prep_value(self, value, connection, prepared=False):
          """Convert value to JSON string before save"""
          try:
              return simplejson.dumps(value)
          except Exception, e:
              raise ValidationError(str(e))
  
new_contents: from django.core.exceptions import ValidationError
  from django.db import models
  from django.utils import simplejson
  
  
  class JSONField(models.TextField):
      """Simple JSON field that stores python structures as JSON strings
      on database.
      """
  
      __metaclass__ = models.SubfieldBase
  
      def to_python(self, value):
          """
          Convert the input JSON value into python structures, raises
          django.core.exceptions.ValidationError if the data can't be converted.
          """
          if self.blank and not value:
              return None
          if isinstance(value, basestring):
              try:
                  return simplejson.loads(value)
              except Exception, e:
                  raise ValidationError(str(e))
          else:
              return value
  
      def validate(self, value, model_instance):
          """Check value is a valid JSON string, raise ValidationError on
          error."""
          super(JSONField, self).validate(value, model_instance)
          try:
              return simplejson.loads(value)
          except Exception, e:
              raise ValidationError(str(e))
  
      def get_prep_value(self, value):
          """Convert value to JSON string before save"""
          try:
              return simplejson.dumps(value)
          except Exception, e:
              raise ValidationError(str(e))
  
subject: Use get_prep_value instead of the database related one. Closes gh-42