Start pulling pub from its own repo.

sdk/lib/_internal/pub/test/global/run/missing_path_package_test.dart

-// 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 'package:path/path.dart' as p;
-import 'package:scheduled_test/scheduled_test.dart';
-
-import '../../../lib/src/io.dart';
-import '../../descriptor.dart' as d;
-import '../../test_pub.dart';
-
-main() {
-  initConfig();
-  integration('errors if the local package does not exist', () {
-    d.dir("foo", [
-      d.libPubspec("foo", "1.0.0"),
-      d.dir("bin", [
-        d.file("foo.dart", "main() => print('ok');")
-      ])
-    ]).create();
-
-    schedulePub(args: ["global", "activate", "--source", "path", "../foo"]);
-
-    schedule(() => deleteEntry(p.join(sandboxDir, "foo")));
-
-    var pub = pubRun(global: true, args: ["foo"]);
-    var path = canonicalize(p.join(sandboxDir, "foo"));
-    pub.stderr.expect('Could not find a file named "pubspec.yaml" in "$path".');
-    pub.shouldExit(1);
-  });
-}