Improve error handling for job fetch

[hbrysiewicz]

When calling SauceWhisk::Jobs.fetch job_id an error occurs in initialize of lib/sauce_whisk/jobs.rb:100. I dug into it and nil was being passed in as the parameters to initialize. This was initiated from the self.fetch on line 46 of same file. When I stepped through it I found that the get job_id was failing with RestClient::ResourceNotFound Exception: 404 Resource Not Found. I was able to discern the job_id I was passing into fetch was incorrect, but there could be better error handling around RestClient exceptions.

[DylanLacey]

Thanks for reporting this. So, get job_id was returning, but not throwing, an exception? That's not cool.

ATM we're using raw RestClient exceptions because there's not much value in wrapping them in a customer SauceLabs exception type. That said, they should definitely be bubbling up to the user if possible.