Some of our wonderful early adopters found a couple bugs in 1.7.8 and some missing API for the new Depends On feature. We decided to get these out before everyone else upgraded.
Thanks early adopters!
Review Board 1.7.9 has an installation fix for some MySQL configurations, new API for Depends On and Blocks fields on review requests, and fixes to the recommended cgit URL for Git repositories.
Release notes are available.