Ruby on Rails Tutorial ２章 scaffoldがgenerate出来ない

Question

前提・実現したいこと

Ruby on Rails Tutorialを行っております。現在、２章でscaffoldをgenerate出来ない問題で立ち止まっています。
入力したコマンド：rails generate scaffold User name:string email:string

発生している問題・エラーメッセージ

(master) $ rails generate scaffold User name:string email:string
ec2-user:~/environment/toy_app (master) $ /home/ec2-user/environment/toy_app/config/application.rb:1:in `<top (required)>': uninitialized constant AbstractController (NameError)
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application.rb:92:in `require'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application.rb:92:in `preload'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application.rb:153:in `serve'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application.rb:141:in `block in run'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application.rb:135:in `loop'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application.rb:135:in `run'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application/boot.rb:19:in `<top (required)>'
        from /usr/local/rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:55:in `require'
        from /usr/local/rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:55:in `require'
        from -e:1:in `<main>'

ec2-user:~/environment/toy_app (master) $ rails generate scaffold User name:string email:string
/home/ec2-user/environment/toy_app/config/application.rb:1:in `<top (required)>': uninitialized constant AbstractController (NameError)
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application.rb:92:in `require'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application.rb:92:in `preload'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application.rb:153:in `serve'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application.rb:141:in `block in run'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application.rb:135:in `loop'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application.rb:135:in `run'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/application/boot.rb:19:in `<top (required)>'
        from /usr/local/rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:55:in `require'
        from /usr/local/rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:55:in `require'
        from -e:1:in `<main>'
ec2-user:~/environment/toy_app (master) $ 

該当のソースコード

app/controllers/application_controller.rbのファイルには下記のコードを入力しました。

class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception

  def hello
    render html: "hello, world!"
  end
end

config/routes.rbのファイルには下記のコードを入力しました

Rails.application.routes.draw do
  root 'application#hello'
end

試したこと

https://stackoverflow.com/questions/28545520/uninitialized-constant-actioncontrollerunknownaction-nameerror-when-starting

上記のQ&Aが一番私が抱えているエラーに近いかなと思いましたが、この通りに行っても、状況は変わらずでした。
もし可能であれば、エラーの対処の方法を教えていただけると幸いです。

どうぞ宜しくお願いいたします。