adding exception info to exported metrics
adding exception info to exported metrics

While monitoring Synapse using the newly exported metrics we realized
there's not enough information about the reported failures to help
investigations. Adding exception name and message to the failure metrics
should provide a big help with that.

Reviewers: e6e744ce641216f4b76692132855533eb0ef9828@ken-experiment

Yelp/synapse,airbnb/synapse