Currently, we only respect the HTTP status codes to detect error conditions. This works for most error conditions – however, this breaks for streaming API endpoints such as pulling an image.

Pulling a non-existant image returns a success status code, however its status events eventually resolve with a message stream like this:

update: {"status":"Pulling repository clue\/does-not-exist"}
update: {"errorDetail":{"message":"Error: image clue\/does-not-exist: not found"},"error":"Error: image clue\/does-not-exist: not found"}

Also refs #4