I would disagree with this report. There are many errors which are effectively silenced by Python, except for being printed on stderr: for example, errors which occur in a __del__ method or a weakref callback (both of which semantically similar to an atexit handler); but also exceptions which terminate a non-main thread.

Python's error code is derived from the return status of the main thread of execution, not counting any kinds of asynchronous exceptions, which are simply displayed and then ignored.

If you want to write a test for errors at program exit, you should check for stderr's contents (by capturing it).