"Again, I don't think this is a good patch. If you want to disable module imports during shutdown, it should be done inside the import machinery, 
not duplicated at every call site."

Ah sorry, I misunderstood your previous comment. I agree that  traceback_finalize.patch is very specific.

Here is a new patch "import_finalization.patch", which block importing new modules (and import again unloaded modules) during finalization.

The full test suite pass with the patch, so at least no unit test tries to import a module during finalization.

> (but I don't necessarily agree that it's a good idea, either)

I'm opening a thread on python-dev to discuss this tricky question.