Currently when the build fails (e.g. due to a missing named export), the message is pretty ugly:

<img width="1033" alt="screen shot 2017-11-04 at 13 12 31" src="https://user-images.githubusercontent.com/810438/32405680-d618d2e6-c161-11e7-9b91-e0241c7c3eed.png">

It would be nice to display the relevant line inline with syntax highlighting, sort of like Babel does it. Maybe Babel's `babel-code-frame` could be helpful (not sure).

To reproduce, fail the build by removing some `export` somewhere and run `yarn build`. (Tip: `yarn build core --type=NODE_DEV` is the fastest way to build just `packages/react/*` and that might be enough to reproduce and iterate on the error message.)

The relevant logic for displaying build errors is probably somewhere in `scripts/rollup/build.js`.

**If you'd like to work on this please comment here, so we don't have many people working on the same thing.**
const shouldSkipBundleType = bundle.bundleTypes.indexOf(bundleType) === -1;
  if (shouldSkipBundleType) {
    return Promise.resolve();
  }
  if (requestedBundleTypes.length > 0) {
    const isAskingForDifferentType = requestedBundleTypes.every(
      requestedType => bundleType.indexOf(requestedType) === -1
    );
    if (isAskingForDifferentType) {
      return Promise.resolve();
    }
  }
  if (requestedBundleNames.length > 0) {
    const isAskingForDifferentNames = requestedBundleNames.every(
      requestedName => bundle.label.indexOf(requestedName) === -1
    );
    if (isAskingForDifferentNames) {
      return Promise.resolve();
    }
  }
  const filename = getFilename(bundle.entry, bundle.global, bundleType);
  const logKey =