rails cannot load such file

Question

前提・実現したいこと

ここに質問の内容を詳しく書いてください。
railsにbootstrapをインストールしてrailsを再起動したところ以下のエラーが発生しました。

発生している問題・エラーメッセージ

Traceback (most recent call last):
        15: from bin/rails:3:in `<main>'
        14: from bin/rails:3:in `load'
        13: from /home/vagrant/rails/todaylesson-dev/bin/spring:15:in `<top (required)>'
        12: from /root/.rbenv/versions/2.5.1/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.           rb:70:in `require'
        11: from /root/.rbenv/versions/2.5.1/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.           rb:70:in `require'
        10: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.0.2/lib/spring           /binstub.rb:31:in `<top (required)>'
         9: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.0.2/lib/spring           /binstub.rb:31:in `load'
         8: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.0.2/bin/spring           :49:in `<top (required)>'
         7: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.0.2/lib/spring           /client.rb:30:in `run'
         6: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.0.2/lib/spring           /client/command.rb:7:in `call'
         5: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.0.2/lib/spring           /client/rails.rb:28:in `call'
         4: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/spring-2.0.2/lib/spring           /client/rails.rb:28:in `load'
         3: from /home/vagrant/rails/todaylesson-dev/bin/rails:8:in `<top (required)>'
         2: from /home/vagrant/rails/todaylesson-dev/bin/rails:8:in `require_relative'
         1: from /home/vagrant/rails/todaylesson-dev/config/boot.rb:4:in `<top (required)>'
/home/vagrant/rails/todaylesson-dev/config/boot.rb:4:in `require': cannot load such file -- b           ootsnap/setup (LoadError)

該当のソースコード

source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }

ruby '2.5.1'

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.2.1'
# Use mysql as the database for Active Record
gem 'mysql2', '>= 0.4.4', '< 0.6.0'
# Use Puma as the app server
gem 'puma', '~> 3.11'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# See https://github.com/rails/execjs#readme for more supported runtimes
# gem 'mini_racer', platforms: :ruby

# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.2'
# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
gem 'turbolinks', '~> 5'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.5'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 4.0'
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use ActiveStorage variant
# gem 'mini_magick', '~> 4.8'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

# Reduces boot times through caching; required in config/boot.rb
#gem 'bootsnap', '>= 1.1.0', require: false
gem 'bootstrap', '~> 4.1.1'
gem 'jquery-rails'
#gem 'kaminari'
#gem 'popper_js', '~> 1.11.1'
#gem 'sass-rails', '~> 5.0'
#gem 'tether-rails'
#gem 'turbolinks', '~> 5'
#gem 'uglifier', '>= 1.3.0'

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
end

group :development do
  # Access an interactive console on exception pages or by calling 'console' anywhere in the code.
  gem 'web-console', '>= 3.3.0'
  gem 'listen', '>= 3.0.5', '< 3.2'
  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'
  gem 'spring-watcher-listen', '~> 2.0.0'
end

group :test do
  # Adds support for Capybara system testing and selenium driver
  gem 'capybara', '>= 2.15'
  gem 'selenium-webdriver'
  # Easy installation and use of chromedriver to run system tests with Chrome
  gem 'chromedriver-helper'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

補足情報（FW/ツールのバージョンなど）

rbenv 1.1.1-39-g59785f6
rails 5

Answer 1

Gemfile の
#gem 'bootsnap', '>= 1.1.0', require: false
の行のコメントアウトを外して、 bundle install してみてください。

bootsnap という gem が config/boot.rb で要求されていますが、それが見つからないといったエラーかと思います。

bootsnap
https://github.com/Shopify/bootsnap