feat: add git error codes to notebooks response

[Panaetius]

closes #1037

/deploy #persist

[olevski]

@Panaetius this looks good to me. I just want to see that the message will really show up when you try to clone but run out of space. If it does not show up this is not really the fault of this PR though. But still it would be nice to double-check.

[RenkuBot]

You can access the deployment of this PR at https://renku-ci-nb-1055.dev.renku.ch

[olevski]

@Panaetius as I suspected there were some issues in the code that are not part of this PR and were there from before that were preventing the error messages from properly surfacing.

I corrected these and I will submit a 2nd PR that will make the necessary changes into this branch. Then we can merge my changes into your branch and merge this branch into master.

Or I can directly commit these changes into your feature branch? If you prefer this let me know and I will close my PR and commit directly here.