Odd traceback error when a variable is not defined

Morning!
We're using the rescue people example and my students are encoutering a kind of odd behaviour in the tracebacks. For instace, if at some point in the code you are using a variable that is not already assigned, instead of launching the common error in python:
line X: Undefined variable 'var' (undefined-variable)
It throughs this kind of error:
line 7: Module 'cv2' has no 'CascadeClassifier' member (no-member)
line 52: Module 'cv2' has no 'cvtColor' member (no-member)
line 52: Module 'cv2' has no 'COLOR_BGR2GRAY' member (no-member)
line 58: Module 'cv2' has no 'rectangle' member (no-member)
Leading to check the import of the libraries when the actual error is not indicated.