py-cachy and tests

[Greg Troxel <gdt%lexort.com@localhost>]

I just got a conflict between py-cachy and py-rnsd because they both
install

  lib/python3.10/site-packages/tests/__init__.py

Obviously *neither* of them should do that, but I can't point to the PEP
rules that say so to file a bug report with cachy.

(I will file a bug with rnsd, and it's in wip anyway.)

In the meantime, should we just patch test out of setup.py so it isn't
installed?  I'll head down that path and commit it unless someone
explains a better approach.