module Devise::Models::Authenticatable

def active_for_authentication?
  true
end

def authenticatable_salt
end

def devise_mailer
  Devise.mailer
end

def inactive_message
  :inactive
end

and inactive_message instead.
However, you should not overwrite this method, you should overwrite active_for_authentication?

if a model should be signed in or not.
find_for_authentication are the methods used in a Warden::Strategy to check
Check if the current object is valid for authentication. This method and

def valid_for_authentication?
  block_given? ? yield : true
end