> It would perhaps be useful if the os.path.expanduser call was added in the cache_from_source() function in importlib?

No: that would mean Python would be doing work that the shell should do. Possibly it would be duplicating the work. Possibly it would be doing it wrong. What if your shell uses ⌂ rather than ~? What if the shell has a different idea of what the home directory is? Remember, you can use Python with any shell, not just Unix/POSIX command-line ones (which is what os.path.expanduser emulates).

Thanks for reporting the issue, though! The separation of concerns definitely isn't obvious at first.