Pip 20 build problems

[igorkramaric]

With Pip 20 Daffodil gets built in a strange way, so importing it's main class doesn't work. As seen here:

  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/app/dpm/apps/dpm_core/models.py", line 26, in <module>
    from daffodil import Daffodil
ImportError: cannot import name 'Daffodil' from 'daffodil' (unknown location)

This is easily reproducible on a local machine.

Until this issue is solved, for Heroku deployments (including tests), an immediate cure is previous buildpack version in the app.json, which is https://github.com/heroku/heroku-buildpack-python#v163

[igorkramaric]

It seems that many people were hit by the same problem: pypa/pip#7620

Probably we should do nothing until solution is found for buildpack

[igorkramaric]

status

pip 20.2.3. does the job, but it's still not used by the latest heroku-buildpack-python
(heroku-buildpack-python currently uses old 20.1.1 pip version as seen here and proven in the buildpack tests)

[tedsmoore]

I can verify this worked for me locally. Required pip uninstall daffodil and I used the --no-cache-dir option when installing (though it might have worked without it), but just documenting the steps here in the event we come across it again.

[igorkramaric]

@tedsmoore pip 20.2.3.? works without the cache switch too. Problem happens only on Heroku builds, because of the buildpack

[Schwarzschild]

Is there a question we should ask Heroku directly with a ticket?

[igorkramaric]

I don't think so. This doesn't regard the core Heroku machinery, it's about open source buildpack: https://github.com/heroku/heroku-buildpack-python