How to update error message displayed when applying to old requisition in Career Center

Summary

When a candidate attempts to apply to a position that is closed, they receive a vague error message. How can we update this message?

Content

When a candidate applies to a position that has since been put on hold or closed they receive the following error message:

"An error occurred. Please try again. If the problem persists please contact the Human Resources department of the company you are applying to. We apologize for the inconvenience."

We would like to customize this message to state that the position is closed, but give them the opportunity to still submit their resume.  How can we customize this message?  [to clarify - this message is received when the candidate goes to the job link then clicks 'Apply Now']