Switch to Flit for packaging

[crccheck]

https://flit.readthedocs.io/en/latest/index.html

[crccheck]

I tested Flit out in https://github.com/crccheck/project_runpy and it was... pretty nice. The downside is you can't pip install -e anymore though

[merwok]

pip install should work, if you have the right pyproject.toml: https://github.com/caravancoop/configstore/blob/master/pyproject.toml (build-system section, the rest is equivalent to flit.ini)

[crccheck]

Thanks, I was going to tackle this soon as cleanup before I start removing support for Django v1 since Django v3 is around the corner.

[crccheck]

looks like pip install -e still doesn't work:

ERROR: File "setup.py" not found. Directory cannot be installed in editable mode: xxxxxxxx
(A "pyproject.toml" file was found, but editable mode currently requires a setup.py based build.)

pypa/pip#6950

[merwok]

There is an ongoing discussion to determine whether pip editable installs should be pluggable (similar to how pip install can call any build system to get a wheel). In the meantime, people have to use lower-level mecanisms specific to the build tool, like python setup.py develop for setuptools or flit install --symlink for flit.

[crccheck]

semantic release solves the problems I had with Poetry, so I'm sticking with Poetry