Trailing slash in URL prevents display of 403 form

If a page has a node access password enabled and a user is given a link to it with a trailing slash, the 403 form will not be displayed so the user will not be able to enter the password to view the node.

This is due to the fact that drupal_lookup_path() cannot not find a matching alias, meaning no node ID can be obtained.

It seems the simple solution is to trim trailing slashes from the URL prior to calling drupal_lookup_path().

Patch incoming.