Fixed regression introduced in r9550

                        except models.FieldDoesNotExist:

                            raise ImproperlyConfigured("%s.list_display[%d], %r is not a callable or an attribute of %r or found in the model %r."

                                % (cls.__name__, idx, field, cls.__name__, model._meta.object_name))

                    else:

                        # getattr(model, field) could be an X_RelatedObjectsDescriptor

                        f = fetch_attr(cls, model, opts, "list_display[%d]" % idx, field)

                        if isinstance(f, models.ManyToManyField):

                            raise ImproperlyConfigured("'%s.list_display[%d]', '%s' is a ManyToManyField which is not supported."