Issue #3268612: StageValidationException does not provide a message based on validation results

package_manager/src/Exception/StageValidationException.php

@@ -49,7 +49,7 @@ class StageValidationException extends StageException {
    *   The results, formatted as plain text.
    */
   public function getResultsAsText(): string {
-    $text = '';
+    $text = $this->message ? $this->message . "\n" : '';
     foreach ($this->getResults() as $result) {
       $messages = $result->getMessages();
       $summary = $result->getSummary();