Respond to https://github.com/jupyterhub/repo2docker/pull/1376

[yuvipanda]

jupyterhub/repo2docker#1376 has been sitting for a month, and is a brand new contribution from someone who is new to the Jupyter ecosystem but seems to be a big contributor to the Julia ecosystem

Suggested Steps

These are purely suggested steps, and need not be followed. Our goal is to see if this PR improves the project, and

1. Setup a local dev environment of repo2docker
2. Validate that the warning the contributor reported is present without this PR
3. Pull julia_project.py: fix Pkg REPL api warning jupyterhub/repo2docker#1376 and test to see if that fixes the issue
4. ??? We have to figure it out from here collectively :) Use your best judgement and ask questions!

Definition of done

• The PR had been responded to in some way
• We write down what we learnt from this process in Round 1: Strategic upstream OSS contributions #5058

[GeorgianaElena]

@agoose77 and I paired on this task and merged the PR today jupyterhub/repo2docker#1376 🎉 🚀

We time-boxed our investigation to 1h and during this time we also managed to do some extensive digging around the Julia command in the PR and we ended up opening a follow-up up task about the possibility of further simplifying it jupyterhub/repo2docker#1383.