[Blogger] Making spree 2.0.3 show your gateway error messages

checkout_controller_decorator.rb

module Spree
  CheckoutController.class_eval do
    def update
      if @order.update_attributes(object_params)
        fire_event('spree.checkout.update')
        return if after_update_attributes
    unless @order.next
      flash[:error] = @order.errors[:base].join("\n")
      redirect_to checkout_state_path(@order.state) and return
    end

    if @order.completed?
      session[:order_id] = nil
      flash.notice = Spree.t(:order_processed_successfully)
      flash[:commerce_tracking] = "nothing special"
      redirect_to completion_route
    else
      redirect_to checkout_state_path(@order.state)
    end
  else
    render :edit
  end
end

order_decorator.rb

module Spree
  Order.class_eval do

    def process_payments!
      if pending_payments.empty?
        raise Core::GatewayError.new Spree.t(:no_pending_payments)
      else
        pending_payments.each do |payment|
          break if payment_total >= total

          payment.process!

          if payment.completed?
            self.payment_total += payment.amount
          end
        end
      end
    rescue Core::GatewayError => e
      result = !!Spree::Config[:allow_checkout_on_gateway_error]
      errors.add(:base, e.message) and return result
    end

  end
end