cocoapods安装报错rubygems/core_ext/kernel_warn (LoadError)，求解决！！！

/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in require': cannot load such file -- rubygems/core_ext/kernel_warn (LoadError) from /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:inrequire’
from /Library/Ruby/Site/2.3.0/rubygems.rb:1395:in ' from :4:inrequire’
from internal:gem_prelude:4:in `internal:gem_prelude’

Macbook pro 10.13.6系统

解决办法：
$ sudo gem update --system 2.7.4