'Reimplement Qt method'

def closeEvent(self, event):

    QMainWindow.closeEvent(self, event)
    if is_pyqt46:
        self.destroyed.emit()
        for editorstack in self.editorwidget.editorstacks[:]:
            if DEBUG_EDITOR:
                print('-->    destroy_editorstack:', editorstack, file=STDOUT)
            editorstack.destroyed.emit()
