Drop support for older Barback versions.

test/transformer/prints_a_transform_interface_error_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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.
 
 library pub_tests;
 
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import '../serve/utils.dart';
 
 final transformer = """
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 
 class RewriteTransformer extends Transformer {
   RewriteTransformer.asPlugin();
 
   String get allowedExtensions => '.txt';
 }
 """;
 
 main() {
-  withBarbackVersions("any", () {
-    integration("prints a transform interface 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("web", [
-          d.file("foo.txt", "foo")
-        ])
-      ]).create();
+  integration("prints a transform interface 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("web", [
+        d.file("foo.txt", "foo")
+      ])
+    ]).create();
 
-      createLockFile('myapp', pkg: ['barback']);
+    createLockFile('myapp', pkg: ['barback']);
 
-      var server = pubServe();
-      server.stderr.expect(emitsLines(
-          "Build error:\n"
-          "Transform Rewrite on myapp|web/foo.txt threw error: Class "
-              "'RewriteTransformer' has no instance method 'apply'."));
-      endPubServe();
-    });
+    var server = pubServe();
+    server.stderr.expect(emitsLines(
+        "Build error:\n"
+        "Transform Rewrite on myapp|web/foo.txt threw error: Class "
+            "'RewriteTransformer' has no instance method 'apply'."));
+    endPubServe();
   });
 }