Re: [infra-tests] use context manager instead of prerun script (#5771)

 [View the complete job log.](https://travis-ci.org/w3c/web-platform-tests/jobs/228389830)

# Firefox (nightly channel) #
Testing web-platform-tests at revision 51e4c93434dd945ca0a651bf9b58d8d4952965d6
Using browser at version BuildID 20170502100421; SourceStamp 48c0fd9c9ec5d68061ea7b59358874ae8da72572
Starting 10 test iterations

View on GitHub: https://github.com/w3c/web-platform-tests/pull/5771#issuecomment-298949986

Received on Wednesday, 3 May 2017 15:41:09 UTC