Add a validator that checks that the lib directory is not empty.

utils/tests/pub/pub_lish_test.dart

Index: utils/tests/pub/pub_lish_test.dart
diff --git a/utils/tests/pub/pub_lish_test.dart b/utils/tests/pub/pub_lish_test.dart
index 58f6a1983ed7f4008f9c3206de1d791237a669b4..a947601d772229b92df61feea78b226ddf001fcb 100644
--- a/utils/tests/pub/pub_lish_test.dart
+++ b/utils/tests/pub/pub_lish_test.dart
@@ -47,12 +47,7 @@ void handleUpload(ScheduledServer server) {
 }
 
 main() {
-  setUp(() {
-    dir(appPath, [
-      libPubspec("test_pkg", "1.0.0"),
-      file("LICENSE", "Eh, do what you want.")
-    ]).scheduleCreate();
-  });
+  setUp(() => normalPackage.scheduleCreate());
 
   test('archives and uploads a package', () {
     var server = new ScheduledServer();