Importing from GitHub is broken

Summary

The recent release of GitLab 8.13.2 seems to have completely broken importing from GitHub.

I'm guessing it's related to !7003 (merged) or it could possibly be !7139 (merged) but that seems much more benign.

Trying to import the same project that I've been using for a while now the progress stops after importing the labels and milestones. I had left if running for around 10-12 hours with no signs of further progress (no merge requests created at all). In the past imports would usually get around 250 imported merge requests.

I haven't been able to test locally in my gdk but I will attempt to reproduce it there soon.