我的mac笔记本安装homebrew出现问题

Question

-bash-3.2$ brew
/usr/local/Library/Homebrew/global.rb:109:in force_encoding': can't modify frozen String (RuntimeError)
from /usr/local/Library/Homebrew/global.rb:109:in'
from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in require'
from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:inrequire'
from /usr/local/Library/brew.rb:16:in `'
这是什么问题