Gutenberg plugin in event CPT

I’m trying to add event CPT to REST API, this way: Adding REST API Support To Existing Content Types with no luck.

When I try this code:

/**
 * Add REST API support to an already registered post type.
 */
add_action( 'init', 'my_custom_post_type_rest_support', 25 );
function my_custom_post_type_rest_support() {
  global $wp_post_types;

  //be sure to set this to the name of your post type!
  $post_type_name = 'event';
  if( isset( $wp_post_types[ $post_type_name ] ) ) {
    $wp_post_types[$post_type_name]->show_in_rest = true;
    // Optionally customize the rest_base or controller class
    $wp_post_types[$post_type_name]->rest_base = $post_type_name;
    $wp_post_types[$post_type_name]->rest_controller_class = 'WP_REST_Posts_Controller';
  }
}

I get some errors:

https://www.dropbox.com/s/iuchg5k02p3i7qm/Captura%20de%20pantalla%202018-02-15%2019.20.37.png?dl=0

Is it possible to add Gutemberg editor to event CPT?

Thank you in advance.