diff -u b/core/lib/Drupal/Core/Database/Install/Tasks.php b/core/lib/Drupal/Core/Database/Install/Tasks.php
--- b/core/lib/Drupal/Core/Database/Install/Tasks.php
+++ b/core/lib/Drupal/Core/Database/Install/Tasks.php
@@ -148,15 +148,15 @@
       }
     }
     // Check for failed results and compile message
-    $messages = [];
+    $message = '';
     foreach ($this->results as $result => $success) {
       if (!$success) {
-        $messages[] = SafeMarkup::isSafe($result) ? $result : SafeMarkup::checkPlain($result);
+        $message = SafeMarkup::isSafe($result) ? $result : SafeMarkup::checkPlain($result);
       }
     }
-    if (!empty($messages)) {
-      $messages_list = '<ul><li>' . implode('</li><li>', $messages) . '</li></ul>';
-      throw new TaskException(SafeMarkup::set(t('Resolve all issues below to continue the installation. For help configuring your database server, see the <a href="https://www.drupal.org/getting-started/install">installation handbook</a>, or contact your hosting provider. !messages_list', ['!messages_list' => $messages_list])));
+    if (!empty($message)) {
+      $message = SafeMarkup::set('Resolve all issues below to continue the installation. For help configuring your database server, see the <a href="https://www.drupal.org/getting-started/install">installation handbook</a>, or contact your hosting provider.' . $message);
+      throw new TaskException($message);
     }
   }