It looks like all of the auth data is empty - maybe you logged into an account which doesn't have permission to install on that repository?

If you email me at colin@webapp.io with your GitHub account name, webapp.io account (if any), and the name of the repository, I can take a look for you.

Ah, I stripped it from the post, didn't want to leave some important tokens on the internets.. :D I removed the authorization and tried again a few minutes later, it ended up working. Probably a temporary problem.