Missing REST call preventing CSE from showing in Plugin DEV Environment

I’m trying to do some development of a simple Bitbucket Plugin but I’m not able to get it running. I think its trying to access the following AJAX call which doesn’t exist.
I assume that after that call it would continue to actually load the CSE but it can’t make it that far. I’ve tried this on both Linux and Windows and have the same issue.

The REST call was a red herring; I overrode the REST call through the Chrome DEV Tools and the extensions still don’t load. This is from the template project so I don’t know what’s wrong.