Fatal error: Uncaught Error: Class "Aws\S3\S3Transfer\AbstractMultipartUploader" not found in C:\WebServer\htdocs\bookshelf\vendor\aws\aws-sdk-php\src\S3\S3Transfer\MultipartUploader.php:25 Stack trace: #0 {main} thrown in C:\WebServer\htdocs\bookshelf\vendor\aws\aws-sdk-php\src\S3\S3Transfer\MultipartUploader.php on line 25