setuptools dependency dropped for python < 3.8

[TryExceptElse]

17c7ca3 changed setup.py to repair setup.py install invocations, but removed the setuptools dependency from wheels built with Python 3.8 or later, regardless of the Python version at the install site.

The new check:

requires = []
if py_version < (3, 8):
    requires.append("setuptools")

checks the current version of python when wheels are built, which will likely not match the version of python on the system where supervisor is installed.

You could perhaps try to inspect the environment to determine if setup.py install is being invoked directly by a user? I haven't tried to do something like that before however.

[mnaberez]

I made a change to this in f82fe73 to clarify the intention.

This is a compromise based on:

• Most users are going to be installing on Python 3.8 or later, where setuptools is not used at runtime by Supervisor anymore.

• With the environment marker (install_requires=["setuptools; python_version < '3.8'"]), installation via setup.py install was completely broken. It's probably also broken on old versions of pip and setuptools before environment markers were introduced, but can otherwise still install Supervisor.

• Users do not want Supervisor to force an installation of setuptools as noted in Replace runtime dependency on setuptools with modern libraries #1578 so install_requires=["setuptools"] won't work.

• Supervisor went for about 15 years without setuptools listed in install_requires=. This didn't generate any tickets for installation problems in all that time because most users installing with pip or setup.py install already have setuptools installed.

• We added setuptools at request of Gentoo maintainers (setup.py: add setuptools to install_requires #1458) who were re-packaging Supervisor. Hopefully, even they are minimally affected by this, since most Gentoo profiles should be running Python 3.8 or later since the last couple of years.

The options that I considered were:

1. Put install_requires=["setuptools"] in setup.py, making it required for everyone, even those who do not need it.
2. Put install_requires=[] in setup.py, which is how it was for 15 years until setup.py: add setuptools to install_requires #1458.
3. Do what I eventually did in f82fe73, which is basically #2 with a little extra help for setup.py install users.

I don't want to try and detect setup.py install because I don't know how to do it reliably and the issue probably also occurs with older pip and setuptools, too.

So, while not ideal, I think #3 above is likely the best we can do until support for legacy Python versions like 2.7 and installation methods like python setup.py install are dropped sometime in the future.

I'm going to close this because I don't think it should hold up a release but feel free to comment further.

[TryExceptElse]

So, while not ideal, I think #3 above is likely the best we can do until support for legacy Python versions like 2.7 and installation methods like python setup.py install are dropped sometime in the future.

I think that is a fair assessment, and f82fe73 clears up the intentions a bit. Thanks for the detailed reply. My use case is admittedly a weird one where I have an embedded system with an old Python version and no setuptools installed by default - it is being brought in specifically for supervisor due to the declared dependency upon it. It should be easy enough for me to explicitly require setuptools be installed though.