move gateway_error require to lib/spree/core.rb

app/controllers/checkout_controller.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require 'open_food_network/address_finder'
-require 'spree/core/gateway_error'
 
 class CheckoutController < Spree::StoreController
   layout 'darkswarm'

app/controllers/spree/admin/orders_controller.rb

@@ -3,7 +3,6 @@ require 'open_food_network/spree_api_key_loader'
 module Spree
   module Admin
     class OrdersController < Spree::Admin::BaseController
-      require 'spree/core/gateway_error'
       include OpenFoodNetwork::SpreeApiKeyLoader
       helper CheckoutHelper
 

lib/spree/core.rb

@@ -50,6 +50,7 @@ require 'spree/core/permalinks'
 require 'spree/core/token_resource'
 require 'spree/core/calculated_adjustments'
 require 'spree/core/product_duplicator'
+require 'spree/core/gateway_error'
 
 ActiveRecord::Base.class_eval do
   include CollectiveIdea::Acts::NestedSet

spec/controllers/spree/admin/orders/payments/payments_controller_refunds_spec.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
-require 'spree/core/gateway_error'
 
 describe Spree::Admin::PaymentsController, type: :controller do
   include StripeHelper

spec/controllers/spree/admin/orders/payments/payments_controller_spec.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require 'spec_helper'
-require 'spree/core/gateway_error'
 
 describe Spree::Admin::PaymentsController, type: :controller do
   let!(:shop) { create(:enterprise) }

spec/models/spree/order_spec.rb

@@ -1,5 +1,4 @@
 require 'spec_helper'
-require 'spree/core/gateway_error'
 
 describe Spree::Order do
   include OpenFoodNetwork::EmailHelper

spec/models/spree/payment_spec.rb

@@ -1,5 +1,4 @@
 require 'spec_helper'
-require 'spree/core/gateway_error'
 
 describe Spree::Payment do
   context 'original specs from Spree' do