The "try jupyterlab" button on jupyter.org failed to create a binder

[moorepants]

Bug description

I'm not quite sure what repository to report this on, but I pressed the "Try JupyterLab" button on jupyter.org and the binder instance failed to build/load. See:

Expected behaviour

Binder should load the instance.

Actual behaviour

Binder doesn't load the instance and reports an error.

How to reproduce

1. Go to '...' jupyter.org
2. Click on '....' "try it in your browser" and then click "try jupyterlab"
3. Scroll down to '....'
4. See error

Your personal set up

• OS:
• Version(s):

• Full environment

# paste output of `pip freeze` or `conda list` here

• Configuration

# jupyterhub_config.py

• Logs