pin setuptools to fix use_2to3

[snacktavish]

https://stackoverflow.com/questions/69100275/error-while-downloading-the-requirements-using-pip-install-setup-command-use-2

Peyotl install was failing - pinning setup tools to an older version fixes it, but doesn't seem like a long term solution...

[jimallman]

I think this is a reasonable fix for now. My quick research on this suggests that the "real" fixes all depend on the upstream projects (i.e. our dependencies) moving past Python 2, or using lib2to3 or similar to handle both python versions. Some other solutions are discussed here, and in PEP 518 (using build-requires to specify the earlier setuptools for a package).