SuspiciousFileOperation

[Pablo849]

class DocumentoGenerico(RegistroMixin):
    def dame_path(self):
        path = ['/']
        try:
            path.append('{}'.format(self.content_type.app_label))
            path.append('{}'.format(self.content_type.model))
            path.append('registro-{}'.format(self.object_id))
        except AttributeError:
            path.append('genericos')
        return path
    documento = PrivateFileField(_('Documento'), upload_subfolder=dame_path, null=True, blank=True)

It returns SuspiciousFileOperation in Django 2.2.20 and upper. Bug or configuration error? Thx.