                  value = data[field_name]
          except KeyError:
              if self.partial:
                  return
              value = [] if self.many else None
  
          if value in (None, '') and self.required:
              raise ValidationError(self.error_messages['required'])
          elif value in (None, ''):
              into[(self.source or field_name)] = None
 
</s> remove                 if is_simple_callable(self.default):
                    native = self.default()
                else:
                    native = self.default
 </s> add                 native = self.get_default_value()
            value = self.get_default_value()
                  value = data[field_name]
          except KeyError:
              if self.partial:
                  return
            value = self.get_default_value()
  
          if value in (None, '') and self.required:
              raise ValidationError(self.error_messages['required'])
          elif value in (None, ''):
              into[(self.source or field_name)] = None
keep keep keep keep replace keep keep keep keep keep
 RelatedField default value handling fixed 
rest_framework/relations.py