Display dependency chain on each Collecting line

[iXce]

This tremendously helps understand why a package is being fetched and
can help investigate and fix dependency resolver backtracking issues
when incoherent constraints/package sets are provided or when new
versions of a package trigger a completely different backtracking
strategy, leading to very hard to debug situations.

[uranusjr]

Can you add a test for this?

[pypa-bot]

Hello!

I am an automated bot and I have noticed that this pull request is not currently able to be merged. If you are able to either merge the master branch into this pull request or rebase this pull request against master then it will eligible for code review and hopefully merging!

[iXce]

Can you add a test for this?

Done! I haven't been sure how to add reviewers explicitly to the PR (I assumed I'd need a well documented issue to back the PR and haven't taken the time to do so)

[iXce]

Hm that remaining PR failure seems to be spurious? 🤔

[uranusjr]

Yes, seems unrelated.

[iXce]

Is there a way to jog the CI to rerun the failed checks?

[uranusjr]

Not needed, we can merge it either way.

[uranusjr]

Please provide a meaningful news fragment. This is a feature, not trivial.

[iXce]

What about this?

[iXce]

Is there something else needed to get this merged? (I cannot add other reviewers it seems, if that's what's needed)

[iXce]

rebased to the latest :) @uranusjr anything I should do to get this merged? I encounter needs for this almost on a daily basis (a very good example is the ongoing sklearn package sunsetting strategy ; knowing which trail of dependencies pulls in sklearn from the install logs would be super useful to fix the requirements)

[pradyunsg]

This will make it harder for me to clean up some stuff later, but we'll cross that bridge when we get there. Thanks @iXce for the PR!

[iXce]

Thanks @pradyunsg !