@trevor, thanks a lot for providing all this info! I’ve finally found the issue, it is a bug in our Bitbucket integration 
Good news is it is fixed, bad news is the fix is not on 9.1.2 
From the pull request, it sounds like this happens on accounts with hidden usernames. Right now, as a workaround, I think you can unhide your username, finish the setup and hide it again. Or if you feel adventurous, you can try our experimental v10 branch which is based off of latest master.