Issue #3248928: Redirect or provide link to apply form for user who started update if accessing start form

src/Form/UpdaterForm.php

@@ -14,7 +14,7 @@ use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Link;
 use Drupal\Core\State\StateInterface;
 use Drupal\Core\Url;
-use Drupal\package_manager\Exception\StageException;
+use Drupal\package_manager\Exception\StageOwnershipException;
 use Drupal\system\SystemManager;
 use Drupal\update\UpdateManagerInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -131,7 +131,7 @@ class UpdaterForm extends FormBase {
             'stage_id' => $stage_id,
           ]);
         }
-        catch (StageException $e) {
+        catch (StageOwnershipException $e) {
           // We already know a stage exists, even if it's not ours, so we don't
           // have to do anything else here.
         }