I've now checked in the working version of the improved error work [1] to master, and I'd like to check it in to 0.12.
The missing commits are: 80587567cc1c48e25fd69a11116175667471e7c8 fa11ada8a804c2353633965ff756b9c5991d1cc6 9d3e995393a918b80aca5ef60061b27a387d053d f066bd520cb2b43524c0e836ee8e8b93e5384c7f Andrew [1] https://issues.apache.org/jira/browse/PROTON-1095
