mondrake
--- a/core/lib/Drupal/Core/Database/Connection.php
+++ b/core/lib/Drupal/Core/Database/Connection.php
    $this->connection = NULL;
  }

+  /**
+   * Returns the client-level database connection object.
+   *
+   * This method should normally be used only within database driver code. Not
+   * doing so constitutes a risk of introducing code that is not database
+   * independent.
+   *
+   * @return object
+   *   The client-level database connection, for example \PDO.
+   */
+  public function getClientConnection(): object {
-  public function getClientConnection(): object {
+  public function getClientConnection(): ?object {