[marmaduke]

Import system is pluggable, so the semantics are there to be customized. Sure, it could be abused (as many things in Python), but an import hook that checks for a vendored dependency with specific version, seems like a reasonable way to resolve the problem above.

> remainder of the file as Ruby and not Python

That's a little excessive

[geofft]

But it changes the semantics of the rest of the language, e.g., if two modules interoperate by passing a type of a third module between themselves, and now there are two copies of that third module, they can't communicate any more.

Getting this right and reliable would be a) a considerable language design project in its own right and b) confusing to users of Python as it is documented, and in particular to people testing their modules locally without pip. It wouldn't be as drastically different a language as Ruby, but it would certainly be a different language.