railsにてknock使用, user無い場合に404が返ってくる

Question

今していること

rails5にてknockを使用し、jwtを用いた認証機能作成
ruby 2.4.5
Rails 5.2.1

実現したこと

login時にuserが無い場合、error messageを返す

問題点

user無い場合404が返ってくる

git hub READ.mdには

Knock responds with a 404 Not Found when the user cannot be found or the password is invalid
```との記載
→knock.rbにexception class追加、しかし404が返ってくる

Knock.setup do |config|

Expiration claim

----------------

How long before a token is expired. If nil is provided, token will

last forever.

Default:

config.token_lifetime = 1.day

Audience claim

--------------

Configure the audience claim to identify the recipients that the token

is intended for.

Default:

config.token_audience = nil

If using Auth0, uncomment the line below

config.token_audience = -> { Rails.application.secrets.auth0_client_id }

Signature algorithm

-------------------

Configure the algorithm used to encode the token

Default:

config.token_signature_algorithm = 'HS256'

Signature key

-------------

Configure the key used to sign tokens.

Default:

config.token_secret_signature_key = -> { Rails.application.secrets.secret_key_base }

config.token_secret_signature_key = -> { Rails.application.credentials.fetch(:secret_key_base) }

If using Auth0, uncomment the line below

config.token_secret_signature_key = -> { JWT.base64url_decode Rails.application.secrets.auth0_client_secret }

Public key

----------

Configure the public key used to decode tokens, if required.

Default:

config.token_public_key = nil

Exception Class

---------------

Configure the exception to be used when user cannot be found.

Default:

config.not_found_exception_class_name = 'ActiveRecord::RecordNotFound' ←ここ追加!!
end

//routes.rb
Rails.application.routes.draw do
post 'user_token' => 'user_token#create'
resources :users

For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html

end

//user_token_controller.rb
class UserTokenController < Knock::AuthTokenController
#skip_before_action :verify_authenticity_token, raise: false
end

//application_controller.rb
class ApplicationController < ActionController::API
include Knock::Authenticable
#undef_method :current_user
end

//user.rb
class User < ApplicationRecord
has_secure_password

validates :firstName, {presence: true}
validates :lastName, {presence: true}
validates :email, {presence: true, uniqueness: true}
validates :password, {presence: true}

def to_token_payload
{
sub: id,
email: email
}
end
end

よろしくお願いいたします。