为什么不从事件循环中弹出异常？

Question

请解释为什么异常不会出现在下面示例中的事件循环中。谢谢。

# -*- coding: utf-8 -*-
from PyQt5.QtWidgets import QMainWindow, QApplication, QPushButton
class MainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__()
        self.pushButton = QPushButton(self)
        self.pushButton.clicked.connect(self.on_click)
        self.t1 = 0
    def on_click(self):
# ZeroDivisionError
        self.t1 = 10 / 0
if __name__ == "__main__":
    import logging
    logging.basicConfig(level = logging.DEBUG, filename = u"test.log", format = u"%(levelname)-8s [%(asctime)s] %(message)s")
    logging.info( u"Start application")
    import sys
    app = QApplication(sys.argv)
    ui = MainWindow()
    ui.show()
    try:
        code = app.exec_()
    except Exception as exc:
        logging.error(exc, exc_info = True)
    logging.info( u"Stop application")
    sys.exit(code)