With declarative config, error "Distribution contains no modules or packages for namespace package"

Attempting to use declarative config for jaraco.itertools, I ran the tests here, and everything looks good except if you inspect the environment, a crucial file is missing, the site-packages/jaraco.itertools-nspkg.pth file.

I tried restoring the namespace package functionality in jaraco/jaraco.itertools@c436dff, but that resulted in this error during the build:

cmdargs: ['/Users/jaraco/code/main/jaraco.itertools/.tox/python/bin/python', '-m', 'pip', 'install', '-e', '/Users/jaraco/code/main/jaraco.itertools[testing]']

Obtaining file:///Users/jaraco/code/main/jaraco.itertools
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
    Complete output from command python setup.py egg_info:
    error in setup command: Distribution contains no modules or packages for namespace package 'jaraco'

I suspect a race condition where the packages discovered by packages= find: aren’t found until after namespace_packages is processed. I suspect the solution is to add support for namespace_packages in declarative config.

[pganssle]

A race condition? Are we doing this stuff in parallel, or do you just mean that the order is not fixed and sometimes they happen in the wrong order?

[jaraco]

I’ve moved the commits from aforementioned repo to this repo here.