Support running executables from dependencies.

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

Index: sdk/lib/_internal/pub/test/run/errors_if_path_in_dependency_test.dart
diff --git a/sdk/lib/_internal/pub/test/run/errors_if_no_executable_is_given_test.dart b/sdk/lib/_internal/pub/test/run/errors_if_path_in_dependency_test.dart
similarity index 62%
copy from sdk/lib/_internal/pub/test/run/errors_if_no_executable_is_given_test.dart
copy to sdk/lib/_internal/pub/test/run/errors_if_path_in_dependency_test.dart
index e92f4c3c0bcef2191278abd2736aad197eb21ba4..81f3a51a12aea14c59925dbb30cdd42f0e0ebed7 100644
--- a/sdk/lib/_internal/pub/test/run/errors_if_no_executable_is_given_test.dart
+++ b/sdk/lib/_internal/pub/test/run/errors_if_path_in_dependency_test.dart
@@ -8,14 +8,21 @@ import '../test_pub.dart';
 
 main() {
   initConfig();
-  integration('Errors if the executable does not exist.', () {
+  integration('Errors if the executable is in a subdirectory in a '
+      'dependency.', () {
+    d.dir("foo", [
+      d.libPubspec("foo", "1.0.0")
+    ]).create();
+
     d.dir(appPath, [
-      d.appPubspec()
+      d.appPubspec({
+        "foo": {"path": "../foo"}
+      })
     ]).create();
 
-    schedulePub(args: ["run"],
+    schedulePub(args: ["run", "foo:sub/dir"],
         error: """
-Must specify an executable to run.
+Can not run an executable in a subdirectory of a dependency.
 
 Usage: pub run <executable> [args...]
 -h, --help    Print usage information for this command.