class ActiveRecord::HasOneThroughCantAssociateThroughCollection

def initialize(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.")
end