make run causes exception

[rossjones]

I just tried a new flask app using yo flask-app and after setup, running make run I get the following error in the browser:

webassets.exceptions.BuildError
BuildError: Nothing to build for <Bundle output=css/css_bower.css, 
filters=[<webassets.filter.compass.Compass object at 0x1109a9b10>], 
contents=()>, is empty

and a stack trace.

After looking through assets.py, it looks like

scss_files = bower_dependencies.get('.scss', [])

returns [] for me. So presumably there is something wrong with my bower_dependencies.json, the entire contents of which is {}.

Looking at bowser_list.js and I am suddenly out of my depth.

Any pointers on how I can solve this?

Edit: Running without debug and the problem goes away.