Propagate elasticsearch errors to the UI
Propagate elasticsearch errors to the UI

Handle and correctly print various errors which
we're being obscured as "Unable to serialise JSON"
errors.
Requests' exceptions also have non-json serializable
characters, and so have to be converted to a safer format.

alexanderlz/redash,vishesh92/redash,denisov-vlad/redash,denisov-vlad/redash,44px/redash,denisov-vlad/redash,imsally/redash,amino-data/redash,stefanseifert/redash,hudl/redash,getredash/redash,amino-data/redash,rockwotj/redash,chriszs/redash,44px/redash,crowdworks/redash,moritz9/redash,M32Media/redash,44px/redash,useabode/redash,chriszs/redash,amino-data/redash,hudl/redash,crowdworks/redash,moritz9/redash,M32Media/redash,crowdworks/redash,rockwotj/redash,moritz9/redash,imsally/redash,EverlyWell/redash,denisov-vlad/redash,vishesh92/redash,rockwotj/redash,hudl/redash,imsally/redash,alexanderlz/redash,useabode/redash,alexanderlz/redash,EverlyWell/redash,getredash/redash,alexanderlz/redash,getredash/redash,amino-data/redash,stefanseifert/redash,getredash/redash,hudl/redash,vishesh92/redash,moritz9/redash,M32Media/redash,stefanseifert/redash,useabode/redash,EverlyWell/redash,imsally/redash,EverlyWell/redash,crowdworks/redash,getredash/redash,chriszs/redash,stefanseifert/redash,denisov-vlad/redash,stefanseifert/redash,rockwotj/redash,useabode/redash,chriszs/redash,M32Media/redash,44px/redash,vishesh92/redash