Building distributions and drawing the Platypus

[brettcannon]

@pradyunsg

If anyone wants to discuss more about (the current effort of) moving code out into dedicated libraries that can be shared easily, please start a new topic.

I created Figuring out what is missing from dedicated packages for supporting downloading and installing a wheel from PyPI to handle the “download a wheel from an index/PyPI for a known package and version and install it” case.