Pin setuptools to <45 to allow installing pipenv on python 2.7

[Benaiah]

Fixes CI failures currently affecting any build-image PRs.

[vbrown608]

I'm not very familiar with the python ecosystem - could you explain what you understood the error to be and why this fixes it?

[Benaiah]

pypa/virtualenv#1493 is the underlying issue that this is taking care of. I'm not a Python expert either, but as I understand it pipenv depends on virtualenv, which in turn requires setuptools. setuptools recently released a new version 45.0.0 which drops support for Python 2. This causes the build to fail because pipenv ends up installing setuptools>=45, which raises an error if installed on Python 2. By explicitly installing a version of setuptools that supports Python 2, we avoid the build failure that occurs on the next line.

I'm not sure why pip is installing a version of setuptools that doesn't support the running version of Python.

[Benaiah]

https://jenkins.ops.netlify.com/blue/organizations/jenkins/build-image/detail/PR-373/1/pipeline is an example of a CI build that failed because of this issue instead of an issue with the PR itself.

[vbrown608]

Thanks for explaining, this seems reasonable. My read of the thread is that maybe some mirror for installing Python packages is not respecting the requirement that virtualenv should use setuptools <45.0.0 with Python 2.7, in which case we won't need this forever.

[vbrown608]

Thanks for tracking this down!