[Feature Request] Improve error messages for Hydra instantiation

[tangbinh]

🚀 Feature Request

Motivation

Is your feature request related to a problem? Please describe.

Many things can go wrong during instantiation, which is expected when the configs are complex and involve many recursive steps. However, the current error messages don't pinpoint exactly where one needs to look at in order to fix the issues, which unnecessarily results in guesswork and frustration.

Pitch

Describe the solution you'd like

As a Hydra user, I often have to go into Hydra code (this line for example) and insert import pdb; pdb.set_trace() just to print out which part of the configs is causing issues. For every problematic config, please print out a part or its whole config object and where it comes from (e.g. file path or Python class). Even better, any exact line number of such a config where the issues are detected can be very helpful.

Describe alternatives you've considered

We have users who are seriously considering not using Hydra instantiation just because it's functioning a bit like a black box. When things don't work, they don't know how to go about fixing it.

cc @jieru-hu

[jieru-hu]

@Jasha10 would you be able to look at this? feel free to re-assign to me if you do not have the bandwidth.

[Jasha10]

Sure, will do!