Last time I checked, our linux workers had both Python 2 and 3 available, but windows only had Python 2 and Mac only Python 3. Can we ensure that all platforms have both versions available?

This affects what platforms some shell integration tests run on. It's possible to rewrite some of the tests as analysis-time tests, or analysis+execution-time tests. But even if I do that, I'll still want something with end-to-end coverage ensuring that py_binarys can in fact locate an interpreter using the (future) default Python toolchain.

For Windows, please ensure that the "py.exe" wrapper is installed, which I believe comes standard with Python 3. It shouldn't matter whether "python.exe" itself is accessible on PATH so long as the wrapper is available. (Whatever tests I add for launching "py.exe" and "python.exe" will probably use a mocked out PATH and fake binaries anyway.)