Report all transformer load errors before exiting.

sdk/lib/_internal/pub/lib/src/utils.dart

Index: sdk/lib/_internal/pub/lib/src/utils.dart
diff --git a/sdk/lib/_internal/pub/lib/src/utils.dart b/sdk/lib/_internal/pub/lib/src/utils.dart
index 24c9ecfc76ed0d6f42d327540f52cd139e2ab65e..d3d2c4aab2fdf6435229d1dd9bc34856348070a8 100644
--- a/sdk/lib/_internal/pub/lib/src/utils.dart
+++ b/sdk/lib/_internal/pub/lib/src/utils.dart
@@ -16,6 +16,7 @@ import 'package:path/path.dart' as path;
 import "package:stack_trace/stack_trace.dart";
 
 import 'exceptions.dart';
+import 'log.dart' as log;
 
 export '../../asset/dart/utils.dart';
 
@@ -124,6 +125,21 @@ Future captureErrors(Future callback(), {bool captureStackChains: false}) {
   return completer.future;
 }
 
+/// Like [Future.wait], but prints all errors from the futures as they occur and
+/// only returns once all Futures have completed, successfully or not.
+///
+/// This will wrap the first error thrown in a [SilentException] and rethrow it.
+Future waitAndPrintErrors(Iterable<Future> futures) {
+  return Future.wait(futures.map((future) {
+    return future.catchError((error, stackTrace) {
+      log.exception(error, stackTrace);
+      throw error;
+    });
+  })).catchError((error, stackTrace) {
+    throw new SilentException(error, stackTrace);
+  });
+}
+
 /// Returns a [StreamTransformer] that will call [onDone] when the stream
 /// completes.
 ///