class ActiveRecord::HasOneThroughCantAssociateThroughCollection

def initialize(owner_class_name = nil, reflection = nil, through_reflection = nil)
  if owner_class_name && reflection && through_reflection
    super("Cannot have a has_one :through association '#{owner_class_name}##{reflection.name}' where the :through association '#{owner_class_name}##{through_reflection.name}' is a collection. Specify a has_one or belongs_to association in the :through option instead.")
  else
    super("Cannot have a has_one :through association.")
  end
end