class ActiveModel::Errors

def full_message(attribute, message)

person.errors.full_message(:name, 'is invalid') # => "Name is invalid"

Returns a full message for a given attribute. 
def full_message(attribute, message)
  return message if attribute == :base
  attr_name = attribute.to_s.tr(".", "_").humanize
  attr_name = @base.class.human_attribute_name(attribute, default: attr_name)
  I18n.t(:"errors.format",
    default:  "%{attribute} %{message}",
    attribute: attr_name,
    message:   message)
end