Drop support for older Barback versions.

test/transformer/fails_to_load_a_transform_with_an_import_error_test.dart

Index: test/transformer/fails_to_load_a_transform_with_an_import_error_test.dart
diff --git a/test/transformer/fails_to_load_a_transform_with_an_import_error_test.dart b/test/transformer/fails_to_load_a_transform_with_an_import_error_test.dart
index 1bf10fd4fa872f25bbe647d62afa45dcde4bbf1e..dfd3553d98479f33fbcd8096c04ca4c0cb2a05a9 100644
--- a/test/transformer/fails_to_load_a_transform_with_an_import_error_test.dart
+++ b/test/transformer/fails_to_load_a_transform_with_an_import_error_test.dart
@@ -13,24 +13,22 @@ import '../serve/utils.dart';
 main() {
   // An import error will cause the isolate API to fail synchronously while
   // loading the transformer.
-  withBarbackVersions("any", () {
-    integration("fails to load a transform with an import error", () {
-      d.dir(appPath, [
-        d.pubspec({
-          "name": "myapp",
-          "transformers": ["myapp/src/transformer"]
-        }),
-        d.dir("lib", [d.dir("src", [
-          d.file("transformer.dart", "import 'does/not/exist.dart';")
-        ])])
-      ]).create();
+  integration("fails to load a transform with an import error", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "transformers": ["myapp/src/transformer"]
+      }),
+      d.dir("lib", [d.dir("src", [
+        d.file("transformer.dart", "import 'does/not/exist.dart';")
+      ])])
+    ]).create();
 
-      createLockFile('myapp', pkg: ['barback']);
-      var pub = startPubServe();
-      pub.stderr.expect("Unable to spawn isolate: Unhandled exception:");
-      pub.stderr.expect(
-          startsWith("Load Error for "));
-      pub.shouldExit(1);
-    });
+    createLockFile('myapp', pkg: ['barback']);
+    var pub = startPubServe();
+    pub.stderr.expect("Unable to spawn isolate: Unhandled exception:");
+    pub.stderr.expect(
+        startsWith("Load Error for "));
+    pub.shouldExit(1);
   });
 }