s3: sometimes message is null and only code is valid

src/storage/s3.js

@@ -133,7 +133,7 @@ async function upload(apiConfig, backupFilePath) {
         stream: passThrough,
         async finish() {
             const [error, data] = await safe(uploadPromise);
-            if (error) throw new BoxError(BoxError.EXTERNAL_ERROR, `Upload error: ${error.message}`);
+            if (error) throw new BoxError(BoxError.EXTERNAL_ERROR, `Upload error: code: ${error.code} message: ${error.message}`); // sometimes message is null
             debug(`Upload finished. ${JSON.stringify(data)}`);
         }
     };