diff --git a/core/core.services.yml b/core/core.services.yml
index 6f6046d..88f026f 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -1169,7 +1169,7 @@ services:
     tags:
       - { name: event_subscriber }
     arguments: ['@config.manager', '@config.storage', '@config.storage.snapshot']
-  exception.neds_installer:
+  exception.needs_installer:
     class: Drupal\Core\EventSubscriber\ExceptionDetectNeedsInstallSubscriber
     arguments: ['@database']
     tags:
diff --git a/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
index a0adb9e..db2df4f5 100644
--- a/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -9,7 +9,6 @@
 use Drupal\Core\Config\BootstrapConfigStorageFactory;
 use Drupal\Core\Config\NullStorage;
 use Drupal\Core\Database\Database;
-use Drupal\Core\Database\DatabaseException;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\Core\DependencyInjection\ServiceModifierInterface;
 use Drupal\Core\DependencyInjection\ServiceProviderInterface;
@@ -17,6 +16,7 @@
 use Drupal\Core\Extension\ExtensionDiscovery;
 use Drupal\Core\File\MimeType\MimeTypeGuesser;
 use Drupal\Core\Http\TrustedHostsRequestFactory;
+use Drupal\Core\Installer\CheckInstalledTrait;
 use Drupal\Core\Language\Language;
 use Drupal\Core\Site\Settings;
 use Symfony\Cmf\Component\Routing\RouteObjectInterface;
@@ -45,6 +45,7 @@
  * container, or modify existing services.
  */
 class DrupalKernel implements DrupalKernelInterface, TerminableInterface {
+  use CheckInstalledTrait;
 
   /**
    * Holds the class used for dumping the container to a PHP array.
@@ -661,57 +662,20 @@ public function handle(Request $request, $type = self::MASTER_REQUEST, $catch =
    *   If the passed in exception cannot be turned into a response.
    */
   protected function handleException(\Exception $e, $request, $type) {
+    if ($this->shouldRedirectToInstaller($e, $this->container ? $this->container->get('database') : NULL)) {
+      return new RedirectResponse($request->getBasePath() . '/core/install.php', 302, ['Cache-Control' => 'no-cache']);
+    }
+
     if ($e instanceof HttpExceptionInterface) {
       $response = new Response($e->getMessage(), $e->getStatusCode());
       $response->headers->add($e->getHeaders());
       return $response;
     }
 
-    if (PHP_SAPI !== 'cli' && $this->isNotInstalledException($e)) {
-      return new RedirectResponse($request->getBasePath() . '/core/install.php', 302, ['Cache-Control' => 'no-cache']);
-    }
-
     throw $e;
   }
 
   /**
-   * Determines if the exception is for a missing or not installed database.
-   *
-   * @param \Exception $e
-   *   The exception to check.
-   *
-   * @return bool
-   *   TRUE if the exception is for a missing or not fully installed database,
-   *   FALSE otherwise.
-   */
-  protected function isNotInstalledException(\Exception $e) {
-    if (!($e instanceof \PDOException || $e instanceof DatabaseException)) {
-      return FALSE;
-    }
-
-    // If we're already in the installer, don't worry about Drupal not being
-    // installed.
-    if (drupal_installation_attempted()) {
-      return FALSE;
-    }
-
-    // Code 1049 is "missing database".
-    if ($e->getCode() == 1049) {
-      return TRUE;
-    }
-
-    // SQLSTATE[42S02] indicates a missing table. Since we should only get here
-    // in case a bootstrap step failed, we assume that whatever table is missing
-    // is missing because the installation is broken, incomplete, or not even
-    // started.
-    if ($e->getCode() == 0 && strpos($e->getMessage(), 'SQLSTATE[42S02]') !== FALSE) {
-      return TRUE;
-    }
-
-    return FALSE;
-  }
-
-  /**
    * {@inheritdoc}
    */
   public function prepareLegacyRequest(Request $request) {
diff --git a/core/lib/Drupal/Core/EventSubscriber/ExceptionDetectNeedsInstallSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/ExceptionDetectNeedsInstallSubscriber.php
index 0a9f58d..b94a0dc 100644
--- a/core/lib/Drupal/Core/EventSubscriber/ExceptionDetectNeedsInstallSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/ExceptionDetectNeedsInstallSubscriber.php
@@ -3,19 +3,17 @@
 namespace Drupal\Core\EventSubscriber;
 
 use Drupal\Core\Database\Connection;
+use Drupal\Core\Installer\CheckInstalledTrait;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 use Symfony\Component\HttpFoundation\RedirectResponse;
 use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
+use Symfony\Component\HttpKernel\KernelEvents;
 
 /**
  * Exception handler to determine if an exception indicates an uninstalled site.
- *
- * Note: The technique here assumes Drupal is installed using SQL, and that
- * sessions are being stored in the database.  If sessions are stored elsewhere
- * or Drupal is being run entirely non-SQL then this detection mechanism may
- * fail.  In such environments it may be necessary to disable this service
- * via the container.
  */
-class ExceptionDetectNeedsInstallSubscriber extends HttpExceptionSubscriberBase {
+class ExceptionDetectNeedsInstallSubscriber implements EventSubscriberInterface {
+  use CheckInstalledTrait;
 
   /**
    * The default database connection.
@@ -24,65 +22,44 @@ class ExceptionDetectNeedsInstallSubscriber extends HttpExceptionSubscriberBase
    */
   protected $connection;
 
-  public function __construct(Connection $connection) {
-    $this->connection = $connection;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function getHandledFormats() {
-    return ['html'];
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  protected static function getPriority() {
-    return 100;
-  }
-
   /**
-   * Determines if Drupal still needs to be installed.
+   * Constructs a new ExceptionDetectNeedsInstallSubscriber.
    *
-   * @return bool
-   *   TRUE if the system still needs to be installed, FALSE otherwise.
+   * @param \Drupal\Core\Database\Connection $connection
+   *   The default database connection.
    */
-  protected function systemNeedsInstall() {
-    // If we're already in the installer, don't worry about Drupal not being
-    // installed.
-    if (PHP_SAPI === 'cli' || drupal_installation_attempted()) {
-      return FALSE;
-    }
-
-    // If there's no sessions table, we assume it means Drupal was never
-    // installed. This may be an incorrect assumption on non-SQL-based
-    // installations.
-    return !$this->connection->schema()->tableExists('session');
+  public function __construct(Connection $connection) {
+    $this->connection = $connection;
   }
 
   /**
-   * Checks if a 404 error is really a sign of an uninstalled Drupal.
-   *
-   * @todo Remove this method in favor of on400() once
-   * https://www.drupal.org/node/2739617 is committed.
+   * Handles errors for this subscriber.
    *
    * @param \Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent $event
    *   The event to process.
    */
-  public function on404(GetResponseForExceptionEvent $event) {
-    return $this->on400($event);
+  public function onException(GetResponseForExceptionEvent $event) {
+    $exception = $event->getException();
+    if ($this->shouldRedirectToInstaller($exception, $this->connection)) {
+      // Only redirect if this is an HTML response (i.e., a user trying to view
+      // the site in a web browser before installing it).
+      $request = $event->getRequest();
+      $format = $request->query->get(MainContentViewSubscriber::WRAPPER_FORMAT, $request->getRequestFormat());
+      if ($format == 'html') {
+        $event->setResponse(new RedirectResponse($request->getBasePath() . '/core/install.php', 302, ['Cache-Control' => 'no-cache']));
+      }
+    }
   }
 
   /**
-   * Checks if a 404 error is really a sign of an uninstalled Drupal.
-   *
-   * @param \Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent $event
+   * Registers the methods in this class that should be listeners.
    *
+   * @return array
+   *   An array of event listener definitions.
    */
-  public function on400(GetResponseForExceptionEvent $event) {
-    if ($this->systemNeedsInstall()) {
-      $event->setResponse(new RedirectResponse($event->getRequest()->getBasePath() . '/core/install.php', 302, ['Cache-Control' => 'no-cache']));
-    }
+  public static function getSubscribedEvents() {
+    $events[KernelEvents::EXCEPTION][] = ['onException', 100];
+    return $events;
   }
+
 }
diff --git a/core/lib/Drupal/Core/Installer/CheckInstalledTrait.php b/core/lib/Drupal/Core/Installer/CheckInstalledTrait.php
new file mode 100644
index 0000000..d00d6d2
--- /dev/null
+++ b/core/lib/Drupal/Core/Installer/CheckInstalledTrait.php
@@ -0,0 +1,80 @@
+<?php
+
+namespace Drupal\Core\Installer;
+
+use Drupal\Core\Database\Connection;
+use Drupal\Core\Database\Database;
+use Drupal\Core\Database\DatabaseException;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
+
+/**
+ * Provides methods for checking if Drupal is already installed.
+ */
+trait CheckInstalledTrait {
+
+  /**
+   * Determines if an exception handler should redirect to the installer.
+   *
+   * @param \Exception $exception
+   *   The exception to check.
+   * @param \Drupal\Core\Database\Connection|null $connection
+   *   (optional) The default database connection. If not provided, a less
+   *   comprehensive check will be performed. This can be the case if the
+   *   exception occurs early enough that a database connection object isn't
+   *   available from the container yet.
+   *
+   * @return bool
+   *   TRUE if the exception handler should redirect to the installer because
+   *   Drupal is not installed yet, or FALSE otherwise.
+   */
+  protected function shouldRedirectToInstaller(\Exception $exception, Connection $connection = NULL) {
+    $exception_to_check = $exception;
+
+    // To avoid unnecessary queries, only act if the exception is one that is
+    // expected to occur when Drupal has not yet been installed. This includes
+    // NotFoundHttpException because an uninstalled site won't have route
+    // information available yet and therefore can return 404 errors.
+    if (!($exception_to_check instanceof \PDOException || $exception_to_check instanceof DatabaseException || $exception_to_check instanceof NotFoundHttpException)) {
+      return FALSE;
+    }
+
+    // Never redirect on the command line.
+    if (PHP_SAPI === 'cli') {
+      return FALSE;
+    }
+
+    // Never redirect if we're already in the installer.
+    if (drupal_installation_attempted()) {
+      return FALSE;
+    }
+
+    // Redirect if there isn't even any database connection information in
+    // settings.php yet, since that means Drupal is not installed.
+    if (!Database::getConnectionInfo()) {
+      return TRUE;
+    }
+
+    // Check for the presence of a database table provided in the hook_schema()
+    // implementation of a required core module. That should always be present
+    // if Drupal is already installed.
+    if (isset($connection)) {
+      try {
+        return !$connection->schema()->tableExists('sessions');
+      }
+      catch (\Exception $e) {
+        // If the query failed, use the exception it failed with for the rest
+        // of the checks in this function; it will be more reliable since
+        // unlike the original exception, we know exactly where it came from.
+        $exception_to_check = $e;
+      }
+    }
+
+    // If we still have an exception at this point, we need to be careful since
+    // we should not redirect if the exception represents an error on an
+    // already-installed site (for example, if the database server went down).
+    // However a database error with code 1049 means "missing database", and it
+    // should be safe to redirect in that case.
+    return ($exception_to_check instanceof \PDOException || $exception_to_check instanceof DatabaseException) && $exception_to_check->getCode() == 1049;
+  }
+
+}