title: eslint undefined named imports
body: <p>I keep running into issues with <code>undefined</code> named imports.  If I mistype the path or filename while importing a named import, I'm not warned.  Then my named import is equal to <code>undefined</code> and it short circuits my reducer or causes some other hard-to-trace problem.</p>
  
  <p>Is there any way to configure eslint to complain about <code>undefined</code> imports?</p>
  
  <pre><code>import { MISSPELLED_CONSTANT } from './constants'
  
  export const myReducer = (state = {}, action) {
    switch(action.type) {
      case MISPELLED_CONSTANT:
        return doSomething(state);
      default:
        return state;
    }
  };
  </code></pre>
  
  <p>Later on in another file:</p>
  
  <p><code>expect(myReducer(undefined, {})).toEqual(initialState)</code></p>
  
  <p>fails because of the bad import.</p>