setuptools requirement in setup.py:install_requires is unsafe

[sevein]

0.5 day

setup.py:install_requires lists setuptools but that's generally considered unsafe. E.g.: it may inadvertently upgrade the setuptools package in the user environment.

I introduced that requirement accidentally back when I addded fido.__version__ in
d6d1071. Likely because a problem with my development setup.

[sevein]

If we eventually identify that fido needs a minimum setuptools version to build correctly, that constraint should be described in the build environment, not in the execution environment. E.g.: it could be listed in requirements/packaging.txt or in the new pyproject.toml like in this example.

An alternative is to use setup_requires. That's what pytest seems to be doing.