Rails5のgem installでnio4rのインストールに失敗する - QiitamacOS Sierra Ruby 2.3 gem install rails --no-ri --no-rdoc したところ以下のエラーで詰まる Building native extensions. This could take a while... ERROR: Error installing rails: ERROR: Failed to build gem native extension. current directory: /Users/{username}/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/nio4r-1.2.1/ext/nio4r /Users/{username}/.rbenv/versions/2.3.1/bin/ruby -r ./siteconf20161031-36453-o4rcff.rb ex
