Mac 安装cocoapod报错

在安装cocoapod的过程中，安装新的ruby版本时报错，如图。

若是跳过更新安装pod，也会报错

/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:in `require'
    from /Library/Ruby/Site/2.3.0/rubygems.rb:1395:in `<top (required)>'
    from <internal:gem_prelude>:4:in `require'
    from <internal:gem_prelude>:4:in `<internal:gem_prelude>'

若添加sudo可以执行下去，但pod setup不可以使用sudo,如图

请问这该怎么解决？