extension-helpers is not detected

[pllim]

In my attempt to apply APE 17 to spacetelescope/synphot_refactor#229 , I ran into a problem with extension-helpers is not detected when:

• Trying to use RTD PR builder: https://readthedocs.org/api/v2/build/10139537.txt
• Trying to run linkcheck on my docs: https://dev.azure.com/spacetelescope/d34890f4-629a-4afe-80df-66fd889d8f45/_apis/build/builds/2766/logs/55

Adding extension-helpers to dependency list for the affected configs did not help. Both logs are a bit different. In the Azure log, it is even more perplexing because it claims to have installed extension-helpers only to proceed to complain that it does not exist:

2019-12-18T22:42:54.8783233Z Successfully installed ... extension-helpers-0.1 ...
2019-12-18T22:42:55.5500628Z Obtaining file:///home/vsts/work/1/s
2019-12-18T22:42:55.5515971Z   Installing build dependencies: started
2019-12-18T22:43:00.1821556Z   Installing build dependencies: finished with status 'done'
2019-12-18T22:43:00.1823954Z   Getting requirements to build wheel: started
2019-12-18T22:43:00.3946548Z   Getting requirements to build wheel: finished with status 'error'
2019-12-18T22:43:00.3948207Z   ERROR: Command errored out with exit status 1:
2019-12-18T22:43:00.3949258Z    command: /opt/hostedtoolcache/Python/3.8.0/x64/bin/python /opt/hostedtoolcache/Python/3.8.0/x64/lib/python3.8/site-packages/pip/_vendor/pep517/_in_process.py get_requires_for_build_wheel /tmp/tmptsto_h83
2019-12-18T22:43:00.3949800Z        cwd: /home/vsts/work/1/s
2019-12-18T22:43:00.3950266Z   Complete output (5 lines):
2019-12-18T22:43:00.3950712Z   
2019-12-18T22:43:00.3951436Z   extension-helpers is not detected, please install with:
2019-12-18T22:43:00.3951900Z   
2019-12-18T22:43:00.3952591Z       pip install -e .

While on RTD:

[rtd-command-info] start-time: 2019-12-18T22:40:31.919856Z, end-time: 2019-12-18T22:40:38.787040Z, duration: 6, exit-code: 1
/home/docs/checkouts/readthedocs.org/user_builds/synphot/envs/229/bin/python -m pip install --upgrade --upgrade-strategy eager --no-cache-dir .[docs]
Processing /home/docs/checkouts/readthedocs.org/user_builds/synphot/checkouts/229
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
  Getting requirements to build wheel: started
  Getting requirements to build wheel: finished with status 'error'
  ERROR: Command errored out with exit status 1:
   command: /home/docs/checkouts/readthedocs.org/user_builds/synphot/envs/229/bin/python /home/docs/checkouts/readthedocs.org/user_builds/synphot/envs/229/lib/python3.7/site-packages/pip/_vendor/pep517/_in_process.py get_requires_for_build_wheel /tmp/tmp2ewv0464
       cwd: /tmp/pip-req-build-gwtv5q4c
  Complete output (5 lines):

  extension-helpers is not detected, please install with:

      pip install -e .

What am I doing wrong?

[astrofrog]

@pllim - this is due to the change in API for extension-helpers, I've left suggestions in https://github.com/spacetelescope/synphot_refactor/pull/229

[pllim]

Oooh, I get it now. It is the custom message that I wrote. :woman_facepalming:

Thanks!