Missing proper 'which' command.

打开终端报错这个

ERROR: Missing proper 'which' command. Make sure it is installed before using RVM!
WARNING:
      Errors sourcing '/Users/ma/.rvm/scripts/base'.
      RVM will likely not work as expected.

百度了一堆解决办法然后删除了rvm不报错了，但是还需要用到rvm，最后找到问题原因是yarn global add xxx引发的，解决办法目前采取了yarn global remove xxx解决问题
更多解决方式参考：
https://issues.jenkins-ci.org/browse/JENKINS-20636?page=com.atlassian.jira.plugin.system.issuetabpanels%3Achangehistory-tabpanel

https://github.com/yarnpkg/yarn/issues/2064