报错：YAML safe loading is not available. Please upgrade psych to a version that supports safe loading (>= 2.0).
ERROR: SSL verification error at depth 1: unable to get local issuer certificate (20)
ERROR: You must add /O=Digital Signature Trust Co./CN=DST Root CA X3 to your local trusted store
ERROR: SSL verification error at depth 2: self signed certificate in certificate chain (19)
ERROR: Root certificate is not trusted (/C=US/O=GeoTrust Inc./CN=GeoTrust Global CA)
ERROR: SSL verification error at depth 2: self signed certificate in certificate chain (19)
ERROR: Root certificate is not trusted (/C=US/O=GeoTrust Inc./CN=GeoTrust Global CA)
查看版本：rvm -v
查询结果：rvm 1.29.3 (latest) by Michal Papis, Piotr Kuczynski, Wayne E. Seguin [https://rvm.io]
获取版本：rvm list known
升级ruby版本：rvm install 2.3.0
错误结果：Error running '__rvm_make -j 1',
please read /Users/jiaweibo/.rvm/log/1510919754_ruby-2.3.0/make.log
There has been an error while running make. Halting the inst
错误结果：fatal: unable to access 'https://github.com/Homebrew/homebrew/': SSLRead() return error -9806 (这个原因是被墙了.)
我的解决办法是弄个代理,重新安装一遍,就OK了
可能是问题所在，其原因在于没有安装Xcode的CommandLineTools工具
执行下面的代码：xcode-select --install
会弹出安装框，一路next，完毕后就可以安装Ruby了
rvm install 2.3.0
最后安装或者升级cocoapods：sudo gem update/install cocoapods