class ActiveRecord::HasManyThroughAssociationPolymorphicThroughError

def initialize(owner_class_name = nil, reflection = nil)
  if owner_class_name && reflection
    super("Cannot have a has_many :through association '#{owner_class_name}##{reflection.name}' which goes through the polymorphic association '#{owner_class_name}##{reflection.through_reflection.name}'.")
  else
    super("Cannot have a has_many :through association.")
  end
end