Re: [infra-tests] show list of errors on inconsistent tests (#4998)

Thanks @jgraham. Just pushed a single commit. 

For posterity, the current unstable output looks like:
![raise_errors](https://cloud.githubusercontent.com/assets/94167/23306334/1e19b8c0-fa71-11e6-9c13-b141e418abb7.png)


View on GitHub: https://github.com/w3c/web-platform-tests/pull/4998#issuecomment-282299917

Received on Friday, 24 February 2017 14:10:59 UTC