how i opening "assigns" after "render :template => ..."?

i have an blunder doing slight applicationcontroller:

rescue_from activerecord::recordnotfound, :with => :not_found

def not_found(exception)
  @exception = exception
  news :template => '/errors/not_found', :status => 404
end

in rails_root/app/views/errors/not_found.html.erb, i have this:

<h1>error 404: found</h1>
<%= debug @exception %>

but @exception always nil there. i've attempted debug assigns, nonetheless that's always {}. assigns copied job render :template? so, i them?

i'm dilemma rails.