title: Replacement for deprecated TYPO3 ErrorpageMessage
body: <p>After the upgrade of the extension tt_board to TYPO3 10 I stumble over deprecation #77164 - ErrorpageMessage and AbstractStandaloneMessage.
  The official page only states that the new Fluid-based ErrorPageController class should be used instead.
  However this controller class is just able to generate a HTML result string for me. But the second half of the job is missing. The HTML output must be shown somehow by TYPO3 in an error dialog raised by an exception.
  Is there any simple solution for this?</p>
  <p>Before:</p>
  <pre><code>use TYPO3\CMS\Core\Messaging\ErrorpageMessage;
  
  ...
  $message = $languageObj-&gt;getLabel('error_no_permission');
  $title = $languageObj-&gt;getLabel('error_access_denied');
  $messagePage =
      GeneralUtility::makeInstance(
          ErrorpageMessage::class,
          $message,
          $title
      );
  $messagePage-&gt;output();
  </code></pre>
  <p>Now:</p>
  <pre><code>use TYPO3\CMS\Core\Controller\ErrorPageController;
  
  ...
  $message = $languageObj-&gt;getLabel('error_no_permission');
  $title = $languageObj-&gt;getLabel('error_access_denied');
  $errorController =
      GeneralUtility::makeInstance(
          ErrorPageController::class
      );
  $content = GeneralUtility::makeInstance(ErrorPageController::class)-&gt;errorAction(
      $title,
      $message
  );
  </code></pre>
  <p>Can I send this $content to a TYPO3 object which will do the error output for the extension?</p>