> Since I wrote tokenize.open(), I can explain why I chose to import builtins :-)

Then it is good to me.

> I would prefer something like traceback_ignore_linecache_error.patch, perhaps combined with a new function that would tell you whether the interpreter is shutting down.

I think we can apply both solutions. Keeping a reference to open will make traceback more usable at exit and ignoring exception will make it more robust in worst case.

And I support the idea about public function or attribute that would tell you whether the interpreter is shutting down. This would be useful in many modules. But this is different issue.