pip 19 added support for something called `pyproject.toml`. Several packages have been setting the option `build-backend = "setuptools.build_meta”` (bcrypt, attrs, jaraco) which seems to be the root of the problem when building from source. Until the community sorts this out I’m inclined to avoid pip 19.
This was causing offline pip installs to fail for some weird reason:
The 'setuptools_scm>=1.15.0' distribution was not found and is required by the application
Even though it is there. v2.x still works.
We `pip download` this file for offline installs. Automat lists this package as a setup_requires, but `pip download` doesn’t resolve these dependencies (distutils will attempt to install them via easy_install when setup.py is invoked).
