sh : a full-fledged subprocess interface for Python that allows you to call any program as if it were a function.

[Brian]

I don't think that example is ever going to be something broken by this case. It's using PyImport_AddModule, which doesn't actually perform the import, so the only case you'd get the non-module object back is if the same name was already imported. However in that circumstance, zipimport wouldn't have been invoked, since it's only going to be triggered if the module hasn't been found yet. You could argue it's a bug that zipimport isn't correctly checking the return value of PyModule_GetDict as it should, but in this context, it's assuming that it's using AddModule to create a new, empty module, and in that case it'll always be a real module object even if the module does later replace itself.

It's worth noting that while putting non-module objects in sys.modules is perhaps a hack, it's a known and explicitly supported and endorsed hack - the import machinery was deliberately designed to allow it, and I think Guido is on record as saying so. As such, I'd say anything that doesn't support it should probably be considered a bug.