解决mac机器上的问题uninitialized constant SystemCommand::Predicable

 Seems to have been fixed by updating it via the install script: 

bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"

from https://www.gitmemory.com/issue/Homebrew/brew/8924/708308655

（https://www.codenong.com/11173458/）