Bump setuptools version.

[bhearsum]

Similar to #2547, setuptools is out of date again, and is causing builds such as https://readthedocs.org/projects/mozilla-balrog/builds/6136328/ to fail.

[bhearsum]

@ericholscher - I'm not sure if you're the right person to pull in, but I see you were involved in #2547 - can you look at this?

[agjohnson]

Thanks for the bump here. Noted in the other PR that updates setuptools, we need to do more testing here and will likely want to wrap this version bump in a feature flag to make sure we don't blow up everyone's builds. I think we can probably roll with this PR instead of #3100, as this is more current.

[bhearsum]

Sounds good to me!

[agronholm]

Why does this need a feature flag? Anyone who wants to upgrade their setuptools can already do this without additional features, by specifying a minimum version in their requirements.txt. That's how I worked around the problem in my own projects.

[agjohnson]

Anyone can upgrade at their own will now. Forcing new setuptools on 40k projects takes operations planning, unless we limit the sample size to who gets the new versions forced on their project. This is where feature flags come in.

Curious, are you forcing the latest setuptools on your projects now without any incident so far?

[agronholm]

I am. Setuptools will have to be upgraded at some point. What good will it do to delay the inevitable?

[agronholm]

Also, what exactly would that feature flag do?

[agjohnson]

@agronholm it allows us to only force the new setuptools version on a small sample. We'll then increase the sample size if no issues are surfacing. All this allows us to limit the amount of breakage and allow operations to move substantially quicker for minor changes like this.

[agronholm]

Oh, I see. I thought it was going to be a voluntary thing. Hence the confusion. So how will you decide who to force it on?

[agjohnson]

Features can be forced on a sample, opt-in, or some mix of the two -- though we lack a strong pattern for opt-in just yet. For this feature, we'll do a random sampling, and anyone else that wants inclusion can get it on their project too.

[agronholm]

Okay, this works for me. Anything as long as it gets done in the end :)