The main idea that comes to mind is to cache a reference to `_frozen_importlib._module_locks` in the interpreter state, and do a key lookup in there (since any in-progress import should have a lock allocated to it).

That would be a separate performance issue though - for this issue, we're on an error handling path, so the speed with which the error gets reported isn't critical (although it does technically slow down try/except import fallback chains).