Exit production build if any errors are in build stats (facebook#859)

* Exit on any errors passed in build stats

* Match console error output in start.js

packages/react-scripts/scripts/build.js

@@ -118,13 +118,27 @@ function printFileSizes(stats, previousSizeMap) {
   });
 }
 
+// Print out errors
+function printErrors(summary, errors) {
+  console.log(chalk.red(summary));
+  console.log();
+  errors.forEach(err => {
+    console.log(err.message || err);
+    console.log();
+  });
+}
+
 // Create the production build and print the deployment instructions.
 function build(previousSizeMap) {
   console.log('Creating an optimized production build...');
   webpack(config).run((err, stats) => {
     if (err) {
-      console.error('Failed to create a production build. Reason:');
-      console.error(err.message || err);
+      printErrors('Failed to compile.', [err]);
+      process.exit(1);
+    }
+
+    if (stats.compilation.errors.length) {
+      printErrors('Failed to compile.', stats.compilation.errors);
       process.exit(1);
     }