ios – Cocoapods没有这样的文件加载错误

LoadError – no such file to load — 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: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/project.rb:4
/Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/installer/analyzer.rb:488:in compute_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:in compute_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:in analyze'
/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:in section'
/Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/installer.rb:93:inresolve_dependencies’
/Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/installer.rb:86:in install!'
/Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/command/project.rb:38:inrun_install_with_update’
/Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/command/project.rb:68:in run'
/Library/Ruby/Gems/1.8/gems/claide-0.3.2/lib/claide/command.rb:206:inrun’
/Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/lib/cocoapods/command.rb:51:in run'
/Library/Ruby/Gems/1.8/gems/cocoapods-0.27.1/bin/pod:19
/usr/bin/pod:23:inload’
/usr/bin/pod:23

我的podfile内容：

pod 'RestKit','~> 0.21.0'

任何帮助将不胜感激！