On Jul 17, 2018, at 5:27 AM, Paul Moore
wrote: There's also a PR cost, in that projects who have enthusiastically adopted pyproject,toml as being a nice "common configuration" location, will be left feeling that maybe that wasn't such a good decision if it's causing them problems like this. Plus, projects like towncrier will need to update their docs (yes, that's a bit ideal world - the reality is that people simply keep doing what they do now, and we get the message out via a gradual process of addressing bug reports and providing the explanation there).
I think that this is the most important reason not to go too crazy here. We should think of breaking changes as having a limited budget for introducing breaking changes, and the question then becomes where do we want to spend our budget? While something being relatively new means that the cost to our budget is smaller, it still has a cost and I just don’t think this is a great place to spend our budget at. On top of that, I don’t think the end result is significantly or meaningfully better for the end users, particularly if we ever get to a world where we isolate everything by default (which would mean that we would have to have an implicit requires of setuptools/wheel anyways).