Trying to use node/%node as a path should fail

Problem/Motivation

In 7.x of page_manager, node/%node has been used as a placeholder for the node argument. It is quite confusing for sitebuilders that this changed to node/%. I think it would be good to validate the path somehow and throw a validation error, when trying to use an invalid path like node/%node.

Proposed resolution

Validate the url.

User interface changes

An error message for the user that the path is invalid.