UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.66 Safari/537.36

Steps to reproduce the problem:
1. Enable ES6 module support in experimental flags
2. Serve an HTML file with the following:
   <script type="module">import 'foo'; console.log('done!');</script>
3. Load the page

What is the expected behavior?
The console should say *something* - either "done!" or an error.  (Note: if 'foo' is changed to '/foo', then the console shows a 404 trying to load the import)

What went wrong?
The console is completely silent.  The network panel is empty since the loader doesn't know how to resolve 'foo', so it doesn't even try.  But as a result, there's no 404 error.  The module just stops evaluating at the invalid import, but doesn't report that anything went wrong.

Did this work before? N/A 

Chrome version: 60.0.3112.66  Channel: n/a
OS Version: 
Flash Version: 

This is a significant problem, since there's a lot of otherwise-browser-compatible code out there that uses babel to rewrite CommonJS-style imports.  If attempting to load such a file in the browser directly, this is exactly what will happen, and so we need a clearer message pointing developers to what went wrong.