Better "module not found" message

Created by: gaearon

This is what I see when I forget to install some npm dependencies:

This is overwhelming and unnecessary. We should have simple messages, like:

These dependencies were not found in node_modules:

  * redux
  * react-redux

Did you forget to run npm install --save for them?

I’m not sure what to do with local file missing errors (i.e. when you import a non-existing file in src). We should probably group them separately but also in a less intimidating way.

I don’t personally plan to work on this so any help is welcome!