ruby-on-rails - Rails 4.0.2で「機械化」を読み込めません

Question

Rails インタラクティブ シェル ( rails c) で、次のようなエラーが表示されます: No such file to load -- Mechanize'when I run require 'mechanize'.

require 'mechanize'不思議なことに、Ruby シェル ( ) で入力してもエラーは発生しませんirb。

出力例を以下に示します。

    rails c 
    Loading development environment (Rails 4.0.2)
    irb(main):001:0> require 'mechanize'
    LoadError: cannot load such file -- mechanize
     from /home/********/.gem/ruby/2.1.0/gems/activesupport-4.0.2/lib/active_support/dependencies.rb:229:in `require'
     from /home/********/.gem/ruby/2.1.0/gems/activesupport-4.0.2/lib/active_support/dependencies.rb:229:in `block in require'
      from /home/********/.gem/ruby/2.1.0/gems/activesupport-4.0.2/lib/active_support/dependencies.rb:214:in `load_dependency'
      from /home/********/.gem/ruby/2.1.0/gems/activesupport-4.0.2/lib/active_support/dependencies.rb:229:in `require'
from (irb):1
      from /home/********/.gem/ruby/2.1.0/gems/railties-4.0.2/lib/rails/commands/console.rb:90:in `start'
      from /home/********/.gem/ruby/2.1.0/gems/railties-4.0.2/lib/rails/commands/console.rb:9:in `start'
      from /home/********/.gem/ruby/2.1.0/gems/railties-4.0.2/lib/rails/commands.rb:62:in `<top (required)>'
      from bin/rails:4:in `require'
      from bin/rails:4:in `<main>'

よろしく