Better error reporting.

[waqasraz]

I think it could be a good idea to report an error when someone user {% render_bundle 'XYZ' %} but the bundle is not declared. Currently, Django displays

http://prnt.sc/byb0u7
http://prnt.sc/byb15c

[ryanhiebert]

Obviously, the KeyError is an error. How would you prefer to see this reported? Just another error type with a more descriptive message, or do you have something else in mind?

[waqasraz]

Something like bundle_name does not exist.

Because my settings file name was "common" and yesterday I was getting error keyerror at / "common". Just saying could be easier for a newbie to webpack-loader.

[owais]

@waqasraz Sounds reasonable. I'd be happy to take a patch :)