Support running executables from dependencies.

sdk/lib/_internal/pub/test/run/nonexistent_dependency_test.dart

Index: sdk/lib/_internal/pub/test/run/nonexistent_dependency_test.dart
diff --git a/sdk/lib/_internal/pub/test/run/nonexistent_script_test.dart b/sdk/lib/_internal/pub/test/run/nonexistent_dependency_test.dart
similarity index 63%
copy from sdk/lib/_internal/pub/test/run/nonexistent_script_test.dart
copy to sdk/lib/_internal/pub/test/run/nonexistent_dependency_test.dart
index cb233b38b4530ea6eea8260ebc8f1ecf1cfcf9c7..10eb68bec357e27a1373b51b3d6aa4a38f7f4f00 100644
--- a/sdk/lib/_internal/pub/test/run/nonexistent_script_test.dart
+++ b/sdk/lib/_internal/pub/test/run/nonexistent_dependency_test.dart
@@ -9,13 +9,14 @@ import 'utils.dart';
 
 main() {
   initConfig();
-  integration('Errors if the script does not exist.', () {
+  integration('Errors if the script is in an unknown package.', () {
     d.dir(appPath, [
       d.appPubspec()
     ]).create();
 
-    var pub = pubRun(args: ["script"]);
-    pub.stderr.expect("Could not find bin/script.dart.");
-    pub.shouldExit(exit_codes.NO_INPUT);
+    var pub = pubRun(args: ["foo:script"]);
+    pub.stderr.expect('Could not find package "foo". Did you forget to add a '
+        'dependency?');
+    pub.shouldExit(exit_codes.DATA);
   });
 }