See "No rebase in progress?" lines in:

http://172.17.131.2/job/btny-pulls-narayana/417/

I think this can happen if you merge the last commit. The rebase is then complete, so "rebase --continue" fails, causing the script to continue it's loop. This is from memory, not had chance to check properly.

Also, it could be due to an upgrade in the CI nodes bringing a new version of git.