Error with CheckRevisionStep

[larsbergstrom]

I discovered that factories.py had not been getting recompiled & we were using an old version. Once buildbot started using it, if CheckRevisionStep is enabled, then we get:
http://build.servo.org/builders/arm32/builds/4619/steps/generic/logs/err.text

For now, I've just commented out adding it to the list, as it's not clear to me how to fix the issue.

cc @aneeshusa @edunham

[aneeshusa]

@larsbergstrom, the build log you linked seems to be an example of CheckRevisionStep working properly by failing the build when the git step doesn't succeed sucessfully - Buildbot seems to handle the Exception cleanly, but let me know if it didn't.

However, the behavior in all of the the linked bugs is a bug, which I've filed #554 for.

[aneeshusa]

One further idea here might be to re-invoke the git step a bounded number of times if we notice it didn't work properly the first time instead of just failing straight away, but I will leave that for a follow-up.

[aneeshusa]

Fix has been deployed and is working.