How do I programmatically delete a node by internal url alias? How do I programmatically delete a node with a specific internal url alias? 

Background: 
We are trying to delete this node so that it can be replaced during an update hook.
After some digging around through the available services and core classes, I have determined you need to get the nid through the path.alias_manager.  Additionally you need to wrap everything in a couple of conditions or you will throw errors if the path does not exist.  (eg. if you are trying to roll this change out to a fleet of sites that might or might not have this path already)

Below is my example code:

  // Check the path is valid before proceeding.
  $pathIsValid = \Drupal::pathValidator()-&gt;isValid('/blog');

  if ($pathIsValid) {
      $alias = \Drupal::service('path.alias_manager')-&gt;getPathByAlias('/blog');
      $params = Url::fromUri("internal:" . $alias)-&gt;getRouteParameters();
      // Get nid.
      $nid = $params[$entity_type];
      $node = Node::load($nid);

      // Check if node exists with the given nid.
      if ($node) {
      $node-&gt;delete();
    }