airbnb/chronos — pull request #320 by depay (2014-12-15 11:22:09+00:00)
Title: Change http code from 200 to 500 when proxying error

Proxying request will throw exception but return 200 if the current
leader crashes, which may affect the judgement of user whether the job
is successful or not. Changing it to 500 to avoid this question.