"Could not find @jupyterlab/builder" on CI in the build job

[krassowski]

I encountered this error over in https://github.com/krassowski/jupyterlab-citation-manager/pull/65 on python -m pip install .[test]. I wonder what am I missing.

• @jupyterlab/builder is in package.json
• locally running python -m pip install .[test] works fine

[krassowski]

It was a missing .yarnrc.yml, thank you @jptio again!