Improve error message for incompatible virtual environment

[zanieb]

The test case for error messages when a virtual environment has a different Python version regressed, undoing the work from #11143 if the interpreter is at the front of the PATH

Originally posted by @zanieb in #11218 (comment)

It's not clear how to do better yet. I think the main problem is we filter the interpreters by version early so we don't know a compatible one is available at all.