Issue #1333292 by mgifford: Fixed Screen-reader users receive no info about...

Issue #1333292 by mgifford: Fixed Screen-reader users receive no info about file upload status / success.

core/modules/file/file.js

@@ -99,7 +99,7 @@ Drupal.file = Drupal.file || {
           '%filename': this.value.replace('C:\\fakepath\\', ''),
           '%extensions': extensionPattern.replace(/\|/g, ', ')
         });
-        $(this).closest('div.form-managed-file').prepend('<div class="messages error file-upload-js-error">' + error + '</div>');
+        $(this).closest('div.form-managed-file').prepend('<div class="messages error file-upload-js-error" aria-live="polite">' + error + '</div>');
         this.value = '';
       }
     }