> whether this would confuse users since they will simply get an ImportError instead of some other error and thus will they be able to realize why there's a problem?

It's the same behaviour we have for any other module on the import path, that doesn't have the right tag. I suppose abi3 is a bit of a special case there, because it's expected to be widely supported...

Also, there is a related problem: Because abi3 is in the supported extension list, setup.py build will build an abi3 extension (which isn't actually abi3), under a pydebug interpreter.