In normal Python (3.x) we always use showerror() from the tkinter module to display an error message but what should I do in PyQt5 to display exactly the same message type as well?
Assuming you are in a QWidget from which you want to display an error message, you can simply use QMessageBox.critical(self, "Title", "Message"), replace self by another (main widget for example) if you are not is a QWidget class.
Python PyQt5: How to show an error message with PyQt5