Fix all the analysis hints in pub.

sdk/lib/_internal/pub/lib/src/oauth2.dart

Index: sdk/lib/_internal/pub/lib/src/oauth2.dart
diff --git a/sdk/lib/_internal/pub/lib/src/oauth2.dart b/sdk/lib/_internal/pub/lib/src/oauth2.dart
index 8de110c00b55f60e55446e2ee1c54cc1e0289d67..d9f068f608f4d6bdf398764c0404ebbca287bda8 100644
--- a/sdk/lib/_internal/pub/lib/src/oauth2.dart
+++ b/sdk/lib/_internal/pub/lib/src/oauth2.dart
@@ -83,7 +83,6 @@ void clearCredentials(SystemCache cache) {
 /// re-run [fn] if a recoverable authorization error is detected.
 Future withClient(SystemCache cache, Future fn(Client client)) {
   return _getClient(cache).then((client) {
-    var completer = new Completer();
     return fn(client).whenComplete(() {
       client.close();
       // Be sure to save the credentials even when an error happens.