The first step: debugging complex issues with Binder is often easier with repo2docker to do the builds and tests locally. You will get a much faster turnaround time and more debug information. This is the same code Binder uses, so if it works locally it will probably work on mybinder.org.
My guess is that it’s crashing due to a lack of X server. I think you need to set up some environment variables and possibly install xvfb. See this SO question for a possibly similar situation.