WIP: Bridged gitaly exceptions

Open Andrew Newdigate requested to merge bridged_gitaly_exceptions into master

What does this MR do?

Reference: https://gitlab.com/gitlab-org/gitaly/issues/588

See https://gitlab.com/gitlab-org/gitaly/merge_requests/358

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?

Edited by Andrew Newdigate