In all honesty, you could continue to maintain a package outside of stdlib, and just require a newer version (which gets installed via the standard packaging tools). This type of behavior isn't well defined in Python, but it's not unrealistic to think it could happen.
For example, let's say there was a new urllib released (its still called urllib). It's now version 2.0, but the stdlib version is 1.0.
If your package said "I need urllib==1.0", it would have know way of understanding that the version was already included within the standard library.
That said, it would download the correct package (assuming it existed) and work just fine.
Other than by introspecting which packages are installed, that is. Most of them will have a VERSION, __version__ or _version attribute which tells you.