cocopods更新

最近把xcode升级到了9.4.1版本，执行pod install的时候，那么问题来了

RuntimeError - [Xcodeproj] Unknown object version.
/usr/local/lib/ruby/gems/2.3.0/gems/xcodeproj-1.5.4/lib/xcodeproj/project.rb:217:in `initialize_from_file'
/usr/local/lib/ruby/gems/2.3.0/gems/xcodeproj-1.5.4/lib/xcodeproj/project.rb:102:in `open'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/installer/analyzer.rb:907:in `block (2 levels) in inspect_targets_to_integrate'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/installer/analyzer.rb:906:in `each'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/installer/analyzer.rb:906:in `block in inspect_targets_to_integrate'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/user_interface.rb:64:in `section'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/installer/analyzer.rb:901:in `inspect_targets_to_integrate'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/installer/analyzer.rb:75:in `analyze'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/installer.rb:243:in `analyze'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/installer.rb:154:in `block in resolve_dependencies'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/user_interface.rb:64:in `section'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/installer.rb:153:in `resolve_dependencies'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/installer.rb:116:in `install!'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/command/install.rb:41:in `run'
/usr/local/lib/ruby/gems/2.3.0/gems/claide-1.0.2/lib/claide/command.rb:334:in `run'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/lib/cocoapods/command.rb:52:in `run'
/usr/local/lib/ruby/gems/2.3.0/gems/cocoapods-1.4.0/bin/pod:55:in `<top (required)>'
/usr/local/bin/pod:23:in `load'
/usr/local/bin/pod:23:in `<main>'


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[!] Oh no, an error occurred.

Search for existing GitHub issues similar to yours:
https://github.com/CocoaPods/CocoaPods/search?q=%5BXcodeproj%5D+Unknown+object+version.&type=Issues

If none exists, create a ticket, with the template displayed above, on:
https://github.com/CocoaPods/CocoaPods/issues/new

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Looking for related issues on cocoapods/cocoapods...
 - Pod init. Unknown object version
   https://github.com/CocoaPods/CocoaPods/issues/7907 [closed] [2 comments]
   3 weeks ago

 - RuntimeError - [Xcodeproj] Unknown object version.
   https://github.com/CocoaPods/CocoaPods/issues/7697 [closed] [27 comments]
   2 weeks ago

 - Unknown object version
   https://github.com/CocoaPods/CocoaPods/issues/7760 [closed] [1 comment]
   21 May 2018

and 41 more at:
https://github.com/cocoapods/cocoapods/search?q=[Xcodeproj]%20Unknown%20object%20version.&type=Issues&utf8=✓

聪明的我：gem install cocoapods --pre 直接干这个命令

Fetching: cocoapods-core-1.5.3.gem (100%)
Successfully installed cocoapods-core-1.5.3
Fetching: cocoapods-downloader-1.2.1.gem (100%)
Successfully installed cocoapods-downloader-1.2.1
Fetching: molinillo-0.6.5.gem (100%)
Successfully installed molinillo-0.6.5
Fetching: atomos-0.1.2.gem (100%)
Successfully installed atomos-0.1.2
Fetching: nanaimo-0.2.6.gem (100%)
Successfully installed nanaimo-0.2.6
Fetching: xcodeproj-1.5.9.gem (100%)
Successfully installed xcodeproj-1.5.9
Fetching: cocoapods-1.5.3.gem (100%)
Successfully installed cocoapods-1.5.3
ERROR:  While executing gem ... (Errno::EACCES)
    Permission denied @ dir_s_mkdir - /usr/local/lib/ruby/gems/2.3.0/doc/cocoapods-core-1.5.3

搞定了不是！