Xcode プロジェクトにポッドを追加しようとしています。このエラーが発生しています：
LoadError - ロードするファイルがありません -- xcodeproj/prebuilt/universal-darwin13.0-1.8.7/xcodeproj_ext /Library/Ruby/Site/1.8/rubygems/core_ext/kernel_require.rb:55:in
gem_original_require' /Library/Ruby/Site/1.8/rubygems/core_ext/kernel_require.rb:55:inrequire' /Library/Ruby /Gems/1.8/gems/xcodeproj-0.14.0/lib/xcodeproj/ext.rb:6 /Library/Ruby/Site/1.8/rubygems/core_ext/kernel_require.rb:55:ingem_original_require' /Library/Ruby/Site/1.8/rubygems/core_ext/kernel_require.rb:55:inrequire' /Library/Ruby/Gems /1.8/gems/xcodeproj-0.14.0/lib/xcodeproj/project.rb:4 /ライブラリ/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/installer/analyzer.rb:488:incompute_target_platforms' /Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/installer/analyzer.rb:485:ineach' /Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/installer/analyzer.rb:485:incompute_target_platforms' /Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/installer/analyzer.rb:55:inanalyze' /Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1 /lib/cocoapods/installer.rb:171:inanalyze' /Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/installer.rb:94:inresolve_dependencies' /Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/user_interface.rb:52:insection' /Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/installer.rb:93:inresolve_dependencies'install!' /Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/command/project.rb:38:in/Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/installer.rb:86:in run_install_with_update' /Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib /cocoapods/command/project.rb:68:run' /Library/Ruby/Gems/1.8/gems/claide-0.3.2/lib/claide/command.rb:206:in実行中' /Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/command.rb:51:run' /Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/bin/pod:19 /usr/bin/pod:23:inロード中' /usr/bin/pod :23
私のポッドファイルの内容：
pod 'RestKit', '~> 0.21.0'
どんな助けでも大歓迎です！