bugfix/2892

[cphyc]

PR Summary

This fixes #2892. The issue is that setup.py install does not call build_ext if ext_modules is empty.
This is fixed by customizing the distribution class and always assume there are some extensions to be built.

I am not quite sure how to test it, but on my local machine pip install . now works from the folder that contains yt, as well as pip install git+file://path/toyt/source/code.

PR Checklist

• pass black --check yt/
• pass isort . --check --diff
• pass flake8 yt/
• pass flynt yt/ --fail-on-change --dry-run -e yt/extern
• New features are documented, with docstrings and narrative docs
• Adds a test for any bugs fixed. Adds tests for new features.

[cphyc]

It looks like it is working on my local machine. Could anyone on Mac/Windows give it a try and install it using?

pip install git+git://github.com/cphyc/yt.git@bugfix/2892

[neutrinoceros]

I'm going to try this on my Mac :)

[neutrinoceros]

I was able to reproduce the error on my Mac and this indeed fixes it; well done !