The same issue arises when an exception is raised during the __init__ execution, rather than in the call argument match phase, and the exception is caught.

class C():
    def __init__(self): self.a = self.b
    def __del__(self): self.a

try:
    C()
except AttributeError): pass
# print same message as before about self.a in __del__

What is different is that if the exception raised within __init__ is not caught, only the normal traceback is printed.