First stab at "pub run" command.

sdk/lib/_internal/pub/test/run/does_not_run_on_transformer_error_test.dart

Index: sdk/lib/_internal/pub/test/run/does_not_run_on_transformer_error_test.dart
diff --git a/sdk/lib/_internal/pub/test/run/does_not_run_on_transformer_error_test.dart b/sdk/lib/_internal/pub/test/run/does_not_run_on_transformer_error_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..8634e1e2674f1b06bc575f2031f3b9ecaf9c0280
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+++ b/sdk/lib/_internal/pub/test/run/does_not_run_on_transformer_error_test.dart
@@ -0,0 +1,64 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+import 'utils.dart';
+
+const SCRIPT = """
+main() {
+  print("should not get here!");
+}
+""";
+
+const TRANSFORMER = """
+import 'dart:async';
+
+import 'package:barback/barback.dart';
+
+class FailingTransformer extends Transformer {
+  FailingTransformer.asPlugin();
+
+  String get allowedExtensions => '.dart';
+
+  void apply(Transform transform) {
+    // Don't run on the transformer itself.
+    if (transform.primaryInput.id.path.startsWith("lib")) return;
+    transform.logger.error('\${transform.primaryInput.id}.');
+  }
+}
+""";
+
+main() {
+  initConfig();
+  withBarbackVersions("any", () {
+    integration('does not run if a transformer has an error', () {
+      d.dir(appPath, [
+        d.pubspec({
+          "name": "myapp",
+          "transformers": ["myapp/src/transformer"]
+        }),
+        d.dir("lib", [
+          d.dir("src", [
+            d.file("transformer.dart", TRANSFORMER)
+          ])
+        ]),
+        d.dir("bin", [
+          d.file("script.dart", SCRIPT)
+        ])
+      ]).create();
+
+      createLockFile('myapp', pkg: ['barback']);
+
+      var pub = pubRun(args: ["script"],
+          transformers: ["myapp/src/transformer"]);
+
+      pub.stderr.expect("[Error from Failing]:");
+      pub.stderr.expect("myapp|bin/script.dart.");
+
+      // Note: no output from the script.
+      pub.shouldExit();
+    });
+  });
+}