This is where we kept seeing failures in #5857. We would look for the URL `/repos/adobe/brackets/issues/false` for non-pull-request travis builds. In this case, instead of `false` from the `TRAVIS_PULL_REQUEST` env var, we expected a PR number.

I forgot that there are 2 kinds of builds: (1) for ordinary commits to any branch and (2) for pull request updates. I don't know why and I haven't found docs to back that up, but it's right there in the build history.