it fails with:
Traceback (most recent call last):
File "setup.py", line 5, in <module>
from setuptools import find_packages, setup
ImportError: cannot import name 'find_packages'
> >> ERROR: py3-attrs: all failed
It appears that it needs a more recent version of setuptools than those
currently bundled with python3 package.
Adding "py3-setuptools" fixed the issue, so I committed it.