'require'：无法加载此类文件'gem'（LoadError）

Question

我意识到有很多与此相同的问题，但是我在解决问题上没有成功。我正在尝试使用gem'vpn'，出于学习目的，我认为我会打开一个全新的项目。按照https://github.com/ronen/vpn（该宝石也位于rubygems.org）上的安装说明进行操作，并在我的代码中要求该宝石，我得到require': cannot load such file -- vpn (LoadError)。

我已经验证了我的版本。 gem env给予

RubyGems Environment:
  - RUBYGEMS VERSION: 2.7.7
  - RUBY VERSION: 2.5.1 (2018-03-29 patchlevel 57) [x86_64-darwin17]
  - INSTALLATION DIRECTORY: /Users/user/.rvm/gems/ruby-2.5.1
  - USER INSTALLATION DIRECTORY: /Users/user/.gem/ruby/2.5.0
  - RUBY EXECUTABLE: /Users/user/.rvm/rubies/ruby-2.5.1/bin/ruby
  - EXECUTABLE DIRECTORY: /Users/user/.rvm/gems/ruby-2.5.1/bin
  - SPEC CACHE DIRECTORY: /Users/user/.gem/specs
  - SYSTEM CONFIGURATION DIRECTORY: /Users/user/.rvm/rubies/ruby-2.5.1/etc
  - RUBYGEMS PLATFORMS:
    - ruby
    - x86_64-darwin-17
  - GEM PATHS:
     - /Users/user/.rvm/gems/ruby-2.5.1
     - /Users/user/.rvm/gems/ruby-2.5.1@global
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => false
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - https://rubygems.org/
  - SHELL PATH:
     - /Users/user/.rvm/gems/ruby-2.5.1/bin
     - /Users/user/.rvm/gems/ruby-2.5.1@global/bin
     - /Users/user/.rvm/rubies/ruby-2.5.1/bin
     - /Users/user/.rvm/bin
     - /Library/Frameworks/Python.framework/Versions/3.7/bin
     - /Library/Frameworks/Python.framework/Versions/3.7/bin
     - /usr/local/bin
     - /usr/bin
     - /bin
     - /usr/sbin
     - /sbin
     - /Applications/Wireshark.app/Contents/MacOS

ruby --version给出ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-darwin17]

在我的gem文件中，我有gem: 'vpn'

gem list确实返回vpn (0.2.1)

任何帮助将不胜感激。预先感谢。

我尝试过的事情：

• 重新安装gem
• 手动将宝石移动到该位置
• Sudo gem安装
• Many: `require': cannot load such file -- "gem_name" (LoadError) after upgrade of ruby/rails
• Rails: LoadError - Cannot load such file (requiring a gem)（我没有服务器在运行）
• gem which cannot find gem despite it being installed
• railties (LoadError) Cannot load such file
• How to check if a gem is installed?

PS我没有rake文件。我尚未设置一个，因为我不太完全确定它是否可以解决我的问题，而我在寻找如何创建一个问题上遇到了问题。