How can I remove messages from Errors object?

I'm trying to handle complex form (nested forms) validation. (Using
this link as http://railscasts.com/episodes/75-complex-forms-part-3 as
how I'm setting up the complex forms.)

Things are working ok, except that I'm getting a few extra messages to
the base that I don't want once the children forms are validated. For
example if dealing with a Project mode and Task models as children...
I'll end up with an extra " Tasks is invalid" message for every Task
that is invalid, which doesn't look good considering the task
validation messages are also showing up.

What I'd like to do is to be able to remove the extra "Tasks is
invalid" messages that show up in my "after_validation" method (unless
someone can recommend a better thing to do?)

The problem is I can't figure out how to remove messages from the
Errors object?

def after_validation
      errors.each do |field,message|
        if field == "tasks"
          #errors >> field ?Is there a way I can remove the message?
        end
      end
  end

A colleague of mine dealt w/ something like this awhile ago. He removed all error messages for tasks and added a custom one that more clearly communicated the situation to the user. He said that you can treat the errors object as an array, so see the docs for Array#delete to delete all of the error messages for tasks.

Regards,
Craig

http://api.rubyonrails.org/classes/ActiveRecord/Errors.html it's not
really an array, but of course probably is backed by one internally.
Looks like someone put in a patch, although when I used edge rails I
didn't see it, so I just manually added the delete method to the
validations.rb as shown in the dif and it's working nicely.

http://dev.rubyonrails.org/ticket/8137

(Being new to rails, does that patch mean it should be in the edge
branch? or does it just mean it's a suggestion to add it?)