Ruby on rails 将Mongoid从4升级到5

我有一个ruby on rails应用程序。 我使用了Mongoid 4.0，现在更新为5.0。 当我运行以下命令时：

rails s

但是得到错误：

config/application.rb:56:in `<class:Application>': uninitialized constant AppName::Application::Moped (NameError)
    from config/application.rb:22:in `<module:ModeTokyo>'
    from config/application.rb:21:in `<top (required)>'
    from vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application.rb:82:in `require'
    from vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application.rb:82:in `preload'
    from vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application.rb:143:in `serve'
    from vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application.rb:131:in `block in run'
    from vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application.rb:125:in `loop'
    from vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application.rb:125:in `run'
    from vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application/boot.rb:18:in `<top (required)>'
    from /Users/nora/.rbenv/versions/2.2.0/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
    from /Users/nora/.rbenv/versions/2.2.0/lib/ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
    from -e:1:in `<main>'

config/application.rb:56:in`'：未初始化的常量AppName:：application:：Moped（NameError）
从config/application.rb:22:in`'
从config/application.rb:21:in`'
来自vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application.rb:82:in'require'
来自vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application.rb:82:in'preload'
来自vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application.rb:143:in'serve'
来自vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application.rb:131:in'block in run'
来自vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application.rb:125:in'loop'
来自vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application.rb:125:in'run'
来自vendor/bundle/ruby/2.2.0/gems/spring-1.3.6/lib/spring/application/boot.rb:18:in`'
来自/Users/nora/.rbenv/versions/2.2.0/lib/ruby/2.2.0/rubygems/core\u ext/kernel\u require.rb:54:in'require'
来自/Users/nora/.rbenv/versions/2.2.0/lib/ruby/2.2.0/rubygems/core\u ext/kernel\u require.rb:54:in'require'
from-e:1:in`'

---

如何修复此错误？

这是因为

config/application.rb

中有一条无效语句，该语句自Mongoid 5以来不起作用

我应该改变这一行：

Moped.logger.level = Logger::DEBUG

进入：

本文件将有助于：

---

这是因为

config/application.rb

中有一条无效语句，该语句自Mongoid 5以来不起作用

我应该改变这一行：

Moped.logger.level = Logger::DEBUG

进入：

本文件将有助于：