How can I override the default error message in Grails?

Question

I have a Person object with a lastName field. The lastName field cannot be blank. When the user submits a form blank value in the lastName field, the error message that the user sees is:

Property [lastName] of class [com.example.Person] cannot be blank

This error message is lame. I want to customize it to something more user friendly, like "The Last Name field cannot be blank"

How do I do that?