          return instance
  
      def save(self):
          """
          Save the deserialized object and return it.
          """
          self.object.save()
 
</s> remove         try:
            instance.full_clean(exclude=self.get_validation_exclusions())
        except ValidationError, err:
            self._errors = err.message_dict
            return None

 </s> add 
    def from_native(self, data, files):
        """
        Override the default method to also include model field validation.
        """
        instance = super(ModelSerializer, self).from_native(data, files)
        if instance:
            return self.full_clean(instance)

          return instance
  
    def from_native(self, data, files):
        """
        Override the default method to also include model field validation.
        """
        instance = super(ModelSerializer, self).from_native(data, files)
        if instance:
            return self.full_clean(instance)

      def save(self):
          """
          Save the deserialized object and return it.
          """
          self.object.save()
keep add keep keep keep keep keep
 Ensure model field validation is performed for ModelSerializers with a custom restore_object method.  Fixes #623. 
rest_framework/serializers.py