Python 3.8 miscompiles the following code:

    $ cat /tmp/wat.py
    enable_debug = False

    if not enable_debug or not __debug__:
        print("you shall not pass!")

    $ python3.7 /tmp/wat.py
    you shall not pass!

    $ python3.8 /tmp/wat.py

(no output is produced.)

This is a distilled example from zope.traversing's codebase (https://github.com/zopefoundation/zope.traversing/issues/13).