only in patch2:
unchanged:
--- a/core/modules/rest/src/Tests/ReadTest.php
+++ b/core/modules/rest/src/Tests/ReadTest.php
@@ -92,7 +92,7 @@ public function testRead() {
     // and hence when there is no matching REST route, the non-REST route is
     // used, but it can't render into application/hal+json, so it returns a 406.
     $this->assertResponse('406', 'HTTP response code is 406 when the resource does not define formats, because it falls back to the canonical, non-REST route.');
-    $expected_message = '{"message":"Not Acceptable.","supported_mime_types":["text\\/html","application\\/vnd.drupal-ajax","application\\/vnd.drupal-dialog","application\\/vnd.drupal-modal"]}';
+    $expected_message = '{"message":"Not Acceptable.","supported_mime_types":["text\\/html","application\\/vnd.drupal-ajax","application\\/vnd.drupal-dialog","application\\/vnd.drupal-modal","application\\/vnd.drupal-ajax-iframeupload","application\\/vnd.drupal-dialog-iframeupload","application\\/vnd.drupal-modal-iframeupload"]}';
     $this->assertIdentical($expected_message, $response);
   }