module Roda::RodaPlugins::ErrorEmail::ClassMethods

def inherited(subclass)

the superclass.
Dup the error email opts in the subclass so changes to the subclass do not affect 
def inherited(subclass)
  super
  opts = subclass.opts[:error_email].dup
  opts[:headers] = opts[:headers].dup.extend(RodaDeprecateMutation)
  subclass.opts[:error_email] = opts.extend(RodaDeprecateMutation)
end