Fix all the analysis hints in pub.

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

Index: sdk/lib/_internal/pub/lib/src/http.dart
diff --git a/sdk/lib/_internal/pub/lib/src/http.dart b/sdk/lib/_internal/pub/lib/src/http.dart
index 3d0453a00ddbd42f60b4c2089b8290e2be1424fa..27e90a074e985a9940c54e3f01640df5c6e9278c 100644
--- a/sdk/lib/_internal/pub/lib/src/http.dart
+++ b/sdk/lib/_internal/pub/lib/src/http.dart
@@ -53,14 +53,6 @@ class _PubHttpClient extends http.BaseClient {
     request.headers[HttpHeaders.USER_AGENT] = "Dart pub ${sdk.version}";
     _logRequest(request);
 
-    // TODO(nweiz): remove this when issue 4061 is fixed.
-    var stackTrace;
-    try {
-      throw null;
-    } catch (_, localStackTrace) {
-      stackTrace = localStackTrace;
-    }
-
     var timeoutLength = HTTP_TIMEOUT;
     var timeoutString = request.headers.remove('Pub-Request-Timeout');
     if (timeoutString == 'None') {
@@ -244,7 +236,7 @@ Map parseJsonResponse(http.Response response) {
   var value;
   try {
     value = JSON.decode(response.body);
-  } on FormatException catch (e) {
+  } on FormatException {
     invalidServerResponse(response);
   }
   if (value is! Map) invalidServerResponse(response);