Deal with Octokit NotFound errors

[daveaglick]

Over time projects will be deleted from GitHub. Right now this breaks the build. Maybe that's a good thing because it'll trigger reviewing and removing the project, but only if the build breaks are actually reviewed (I missed one over a weekend for several days).

A better alternative might be to gracefully handle the failure and somehow report it. Even better would be to automate a PR that removes the project for us (along with a disclaimer to manually verify).