Unfatal rendering of repository policy transactions
Summary: Fixes T4919. There's some special casing in Diffusion for CAN_PUSH right now, just accommodate that until things get more general.
Test Plan: Viewed a repository edit screen with a custom policy transaction. Clicked the link to view it.
Reviewed By: btrahan
Maniphest Tasks: T4919
Differential Revision: https://secure.phabricator.com/D8898