pub site: update dependencies and fix analyzer

app/test/backend_test_utils.dart

Index: app/test/backend_test_utils.dart
diff --git a/app/test/backend_test_utils.dart b/app/test/backend_test_utils.dart
index 6953f9c07af377810e4a78d09f875a1d1869299f..15bf7b8e8d78826aed6a784ca7a5fec15a2bedb3 100644
--- a/app/test/backend_test_utils.dart
+++ b/app/test/backend_test_utils.dart
@@ -194,6 +194,9 @@ class TarballStorageMock implements TarballStorage {
     if (uploadViaTempObjectFun == null) throw 'no uploadViaTempObjectFun';
     return uploadViaTempObjectFun(guid, package, version);
   }
+
+  Future remove(String package, String version) =>
+      throw new UnimplementedError();
 }
 
 class UploadSignerServiceMock implements UploadSignerService {