Add a "global activate" command to pub.

sdk/lib/_internal/pub/lib/src/utils.dart

Index: sdk/lib/_internal/pub/lib/src/utils.dart
diff --git a/sdk/lib/_internal/pub/lib/src/utils.dart b/sdk/lib/_internal/pub/lib/src/utils.dart
index 24c9ecfc76ed0d6f42d327540f52cd139e2ab65e..1c447c24142ddbb342cd40c55ce57f25d24f3d9c 100644
--- a/sdk/lib/_internal/pub/lib/src/utils.dart
+++ b/sdk/lib/_internal/pub/lib/src/utils.dart
@@ -819,3 +819,11 @@ void fail(String message, [innerError, StackTrace innerTrace]) {
     throw new ApplicationException(message);
   }
 }
+
+/// Throw a [DataException] with [message] to indicate that the command has
+/// failed because of invalid input data.
+///
+/// This will report the error and cause pub to exit with [exit_codes.DATA].
+void dataError(String message) {
+  throw new DataException(message);
+}