Support activating packages from local paths.

sdk/lib/_internal/pub/test/global/activate/path_does_not_exist_test.dart

Index: sdk/lib/_internal/pub/test/global/activate/path_does_not_exist_test.dart
diff --git a/sdk/lib/_internal/pub/test/cache/repair/empty_cache_test.dart b/sdk/lib/_internal/pub/test/global/activate/path_does_not_exist_test.dart
similarity index 56%
copy from sdk/lib/_internal/pub/test/cache/repair/empty_cache_test.dart
copy to sdk/lib/_internal/pub/test/global/activate/path_does_not_exist_test.dart
index 9f398b7635f3a481c460620429cfe73db3282b6e..3170c91f55910f90ee492421cf3b278319090833 100644
--- a/sdk/lib/_internal/pub/test/cache/repair/empty_cache_test.dart
+++ b/sdk/lib/_internal/pub/test/global/activate/path_does_not_exist_test.dart
@@ -2,15 +2,13 @@
 // 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 '../../test_pub.dart';
 
 main() {
   initConfig();
-  integration('does nothing if the cache is empty', () {
-    // Repair them.
-    schedulePub(args: ["cache", "repair"],
-        output: "No packages in cache, so nothing to repair.");
+  integration('fails if path does not exist', () {
+    schedulePub(args: ["global", "activate", "--source", "path", "nope"],
+        error: 'Could not find a file named "pubspec.yaml" in "nope".',
+        exitCode: 1);
   });
 }