Ok, figured it out, but it looks like you already added the CB pubkey to your account as a deploy key, so we can't re-use it 'til it's gone from there, I think.
I've deleted my test account and added the same key as a Deploy Key to the new job. No complaints from GitHub so far...
https://jclouds.ci.cloudbees.com/job/EXPERIMENTAL-mirror-apache-to-jclouds/5/console https://github.com/jclouds/test-mirror ap
