Okay, it does not work in Qt4 version either.

Traceback (most recent call last):
  File "/home/Hin-Tak/my-git/skia-python-examples/glwidget_abouttobedestroyed.py", line 38, in <module>
    main()
    ~~~~^^
  File "/home/Hin-Tak/my-git/skia-python-examples/glwidget_abouttobedestroyed.py", line 33, in main
    window = MainWindow()
  File "/home/Hin-Tak/my-git/skia-python-examples/glwidget_abouttobedestroyed.py", line 29, in __init__
    self.setCentralWidget(MyOpenGLWidget(self))
                          ~~~~~~~~~~~~~~^^^^^^
  File "/home/Hin-Tak/my-git/skia-python-examples/glwidget_abouttobedestroyed.py", line 10, in __init__
    self.aboutToBeDestroyed.connect(self.cleanupGL)
    ^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'MyOpenGLWidget' object has no attribute 'aboutToBeDestroyed'

Author: HinTak

glwidget_abouttobedestroyed.py

@@ -1,6 +1,6 @@
-from PyQt5.QtWidgets import QApplication, QMainWindow
-from PyQt5.QtOpenGL import QGLWidget
-from PyQt5.QtCore import pyqtSlot
+from PyQt4.QtGui import QApplication, QMainWindow
+from PyQt4.QtOpenGL import QGLWidget
+from PyQt4.QtCore import pyqtSlot
 import sys
 
 class MyOpenGLWidget(QGLWidget):