[Distutils] Finishing up PEP 517

[Donald Stufft]

> 
> On Jun 16, 2017, at 11:08 PM, Nathaniel Smith <njs at pobox.com> wrote:
> 
> (because the legacy setup.py
> command errors out, because the build_sdist hook is missing, because
> the build_sdist hook errors out...); probably falling back on
> shutil.copytree.


Ah okay. This is where the disconnect was. I assumed if a project was using a PEP 517 build tool the result of a build_sdist failure (or a build_wheel failure) would be surfacing an error to the end user, not some sort of fallback.