Add debug messages for "createLabel" and "addLabels" failures in "createOrAddLabel"

[sogame]

When using createOrAddLabel sometimes I'm getting a failure:

RequestError [HttpError]: Validation Failed: {"resource":"Label","code":"already_exists","field":"name"}

Indeed the label already exists, and looking at the code for createOrAddLabel I think this could only happen if api.issues.listLabelsForRepo throws an exception.

I think it would be useful to add try/catch statements and debug messages when calling api.issues.createLabel and api.issues.addLabels to get more information and avoid Danger failing when these requests fail (same as done for api.issues.listLabelsForRepo).

[sogame]

Build is failing, but looks like it was failing in a previous pr: #1013

[orta]

This seems very reasonable to me 👍

[rohit-gohri]

Build is failing, but looks like it was failing in a previous pr: #1013

Deleted Travis cache and restarted master build, it passed now.

[sogame]

Hi @orta, I know this is a tiny change, but would it be possible to publish a new release of Danger JS? 😇

[peril-staging]

Thanks for the PR @sogame.

This PR has been shipped in v9.4.0 - CHANGELOG.

[orta]

Yeah, it didn't look the others were coming anytime too soon

[sogame]

Thanks a lot @orta 🙇