Problem launching Binder on startup

[leewujung]

This is discovered from #48 and needs investigation.

From @ctuguinay :

There's also the backend problems with Binder (unrelated to the computation resources they offer in the notebooks themselves) that I noticed when I last tried to launch Binder and even now. Here's what I current see when I try to launch it:

The Build Logs with the Internal Server Error with nothing below it isn't very helpful either.