I have recently reinstalled ruby 2.1.2 like so since I wanted to install a gem (ruby-debug-ide)
ruby-debug-ide
sudo rvm reinstall 2.1.2 --disable-binary --with
This solved my problem:
Replace libreadline.{version}.dylib with the version you are getting error for:
ln -s /usr/local/opt/readline/lib/libreadline.dylib /usr/local/opt/readline/lib/libreadline.7.dylib