grails No such property: errors for command objects

The problem

When attempting to add a custom error message to a command object (non-domain object), I was trying to do this in the following way:

commandObject.errors.reject(null, "Some error msg")

However, when I go to execute the application, I received the following error:

No such property: errors

 It turns out, that the errors property of a command object is not always created.

The Solution

To have grails automatically create the errors object, the command objects must be annotated as "@Validateable"

and in the Config.groovy file add the following line:

grails.validateable.packages=['package.name.containing.command.object']

References: 

http://grails.1312388.n4.nabble.com/Possible-problem-with-Controller-Commands-and-errors-td2257062.html

http://www.grails.org/doc/1.3.7/guide/7.%20Validation.html#7.5%20Validation%20Non%20Domain%20and%20Command%20Object%20Classes