Rails无法安装gem'und'

Question

每当我尝试：$ gem install unf时，我都会收到此错误：

ERROR:  While executing gem ... (NoMethodError)
    undefined method `spec' for nil:NilClass

我甚至尝试添加这些库

sudo apt-get install build-essential openssl libreadline6 libreadline6-dev curl git-core     zlib1g zlib1g-dev libssl-dev libyaml-dev libsqlite3-0 libsqlite3-dev sqlite3 libxml2-dev libxslt-dev autoconf libc6-dev ncurses-dev automake libtool bison

但没有雪茄，知道我该怎么办？

Answer 1

sudo REALLY_GEM_UPDATE_SYSTEM=TRUE gem update --system

工作