Xcode升级9.3之后, cocoapods命令报错

[!] Oh no, an error occurred.

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https://github.com/CocoaPods/CocoaPods/search?q=%5BXcodeproj%5D+Unknown+object+version.&type=Issues

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Looking for related issues on cocoapods/cocoapods...

 - RuntimeError - [Xcodeproj] Unknown object version.

   https://github.com/CocoaPods/CocoaPods/issues/7697 [closed] [16 comments]

   a day ago

 - RuntimeError - [Xcodeproj] Unknown object version.

   https://github.com/CocoaPods/CocoaPods/issues/7712 [closed] [9 comments]

   2 weeks ago

 - Unknown object version

   https://github.com/CocoaPods/CocoaPods/issues/7760 [closed] [1 comment]

   a day ago

and 38 more at:

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

Pod版本与Xcode版本不兼容

需要升级Xcode

sudo gem update --system

sudo gem install -n /usr/local/bin cocoapods