Run pub tests against older versions of barback.

sdk/lib/_internal/pub/test/transformer/fails_to_load_a_non_existent_transform_test.dart

Index: sdk/lib/_internal/pub/test/transformer/fails_to_load_a_non_existent_transform_test.dart
diff --git a/sdk/lib/_internal/pub/test/transformer/fails_to_load_a_non_existent_transform_test.dart b/sdk/lib/_internal/pub/test/transformer/fails_to_load_a_non_existent_transform_test.dart
index e78b8baec82a41fd1c8ead560d4ff4f5e58fe486..57456c6063680ef5c2e9fd5873e87c98d7247512 100644
--- a/sdk/lib/_internal/pub/test/transformer/fails_to_load_a_non_existent_transform_test.dart
+++ b/sdk/lib/_internal/pub/test/transformer/fails_to_load_a_non_existent_transform_test.dart
@@ -10,17 +10,19 @@ import '../serve/utils.dart';
 
 main() {
   initConfig();
-  integration("fails to load a non-existent transform", () {
-    d.dir(appPath, [
-      d.pubspec({
-        "name": "myapp",
-        "transformers": ["myapp/transform"]
-      })
-    ]).create();
+  withBarbackVersions("any", () {
+    integration("fails to load a non-existent transform", () {
+      d.dir(appPath, [
+        d.pubspec({
+          "name": "myapp",
+          "transformers": ["myapp/transform"]
+        })
+      ]).create();
 
-    var pub = startPubServe();
-    pub.stderr.expect(
-        'Transformer library "package:myapp/transform.dart" not found.');
-    pub.shouldExit(1);
+      var pub = startPubServe();
+      pub.stderr.expect(
+          'Transformer library "package:myapp/transform.dart" not found.');
+      pub.shouldExit(1);
+    });
   });
 }