Ruby Rails 3上的i18n任务命令错误？

我正在构建一个使用gem的新Rails应用程序，但当我运行命令

i18n tasks

时，此输出显示：

/home/user-pc/.rvm/gems/ruby-1.9.3-p392@product/gems/i18n-tasks-0.5.1/lib/i18n/tasks/plural_keys.rb:3:in `<module:PluralKeys>': uninitialized constant I18n::Tasks::PluralKeys::Set (NameError)
    from /home/user-pc/.rvm/gems/ruby-1.9.3-p392@product/gems/i18n-tasks-0.5.1/lib/i18n/tasks/plural_keys.rb:2:in `<top (required)>'
    from /home/user-pc/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site_ruby/1.9.1/rubygems/core_ext/kernel_require.rb:73:in `require'
    from /home/user-pc/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site_ruby/1.9.1/rubygems/core_ext/kernel_require.rb:73:in `require'
    from /home/user-pc/.rvm/gems/ruby-1.9.3-p392@product/gems/i18n-tasks-0.5.1/lib/i18n/tasks/base_task.rb:5:in `<top (required)>'
    from /home/user-pc/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site_ruby/1.9.1/rubygems/core_ext/kernel_require.rb:73:in `require'
    from /home/user-pc/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site_ruby/1.9.1/rubygems/core_ext/kernel_require.rb:73:in `require'
    from /home/user-pc/.rvm/gems/ruby-1.9.3-p392@product/gems/i18n-tasks-0.5.1/lib/i18n/tasks.rb:20:in `<top (required)>'
    from /home/user-pc/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site_ruby/1.9.1/rubygems/core_ext/kernel_require.rb:73:in `require'
    from /home/user-pc/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site_ruby/1.9.1/rubygems/core_ext/kernel_require.rb:73:in `require'
    from /home/user-pc/.rvm/gems/ruby-1.9.3-p392@product/gems/i18n-tasks-0.5.1/bin/i18n-tasks:4:in `<top (required)>'
    from /home/user-pc/.rvm/gems/ruby-1.9.3-p392@product/bin/i18n-tasks:23:in `load'
    from /home/user-pc/.rvm/gems/ruby-1.9.3-p392@product/bin/i18n-tasks:23:in `<main>'

/home/user pc/.rvm/gems/ruby-1.9.3-p392@product/gems/i18n-tasks-0.5.1/lib/i18n/tasks/mulral_-keys.rb:3:in`'：未初始化常量i18n:：tasks:：PluralKeys:：Set（NameError）
来自/home/user pc/.rvm/gems/ruby-1.9.3-p392@product/gems/i18n-tasks-0.5.1/lib/i18n/tasks/multiple_key.rb:2:in`'
来自/home/user pc/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site\u ruby/1.9.1/rubygems/core\u ext/kernel\u require.rb:73:in'require'
来自/home/user pc/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site\u ruby/1.9.1/rubygems/core\u ext/kernel\u require.rb:73:in'require'
来自/home/user pc/.rvm/gems/ruby-1.9.3-p392@product/gems/i18n-tasks-0.5.1/lib/i18n/tasks/base_task.rb:5:in`'
来自/home/user pc/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site\u ruby/1.9.1/rubygems/core\u ext/kernel\u require.rb:73:in'require'
来自/home/user pc/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site\u ruby/1.9.1/rubygems/core\u ext/kernel\u require.rb:73:in'require'
来自/home/user pc/.rvm/gems/ruby-1.9.3-p392@product/gems/i18n-tasks-0.5.1/lib/i18n/tasks.rb:20:in`'
来自/home/user pc/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site\u ruby/1.9.1/rubygems/core\u ext/kernel\u require.rb:73:in'require'
来自/home/user pc/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site\u ruby/1.9.1/rubygems/core\u ext/kernel\u require.rb:73:in'require'
来自/home/user pc/.rvm/gems/ruby-1.9.3-p392@product/gems/i18n-tasks-0.5.1/bin/i18n任务：4:in`'
来自/home/user pc/.rvm/gems/ruby-1.9.3-p392@product/bin/i18n任务：23:在“加载”中
来自/home/user pc/.rvm/gems/ruby-1.9.3-p392@product/bin/i18n任务：23:in`'

---

主要问题是什么？为什么我不能在文件中运行这些命令？

主要问题是如何运行

i18n任务。文件上说我可以执行：

i18n-tasks

但是我直接执行的命令失败了。要正常工作，该命令需要以以下方式运行：

bundle exec i18n-tasks

这就是全部