Ch 4: Save file error message fails

[btuftin]

The call to qtw.QMessageBox.critical(f"Could not open file: {e}") fails with error
TypeError: critical(QWidget, str, str, buttons: Union[QMessageBox.StandardButtons, QMessageBox.StandardButton] = QMessageBox.Ok, defaultButton: QMessageBox.StandardButton = QMessageBox.NoButton): not enough arguments

critical requires a reference to parent and a title, so this works:
qtw.QMessageBox.critical(self, "Error", f"Could not load file: {e}")

[alandmoore]

Thanks for reporting this. Fixed by 565b8e3