How to add a validation rule to require a File Attachment

Summary:

We have a number of files that need to be uploaded. I tried to add a validation rule to check on a specific Action but in the Components to Validate any attributes of File Attachment are not selectable.

Content (please ensure you mask any confidential information):

I can add an advanced condition to check if the file is blank. But am unable to add it to the Components to Validate.

Version (include the version you are using, if applicable):

23 D Patch 3

Code Snippet (add any code snippets that support your topic, if applicable):