rvm install ruby-2.3.0
this gave this error:
more /Users/alex/.rvm/log/1600191501_ruby-2.3.0/rubygems.install.log
[2020-09-15 12:46:13] /Users/alex/.rvm/rubies/ruby-2.3.0/bin/ruby
current path: /Users/alex/.rvm/src/rubygems-3.0.8
GEM_HOME=/Users/alex/.rvm/gems/ruby-2.7.1
PATH=/usr/local/opt/coreutils/bin:/usr/local/opt/pkg-config/bin:/usr/local/opt/libtool/bin:/usr/local/opt/automake/bin:/usr/local/opt/autoconf/bin:/Users/alex/.cabal/bin:/Users/alex/.ghcup/bin:/Users/alex/.nvm/versions/node/v8.11.3/bin:/Users/alex/.nix-profile/bin:/Users/alex/bin:/Users/alex/.rvm/gems/ruby-2.7.1/bin:/Users/alex/.rvm/gems/ruby-2.7.1@global/bin:/Users/alex/.rvm/rubies/ruby-2.7.1/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/TeX/texbin:/Library/Apple/usr/bin:/Users/alex/.rvm/bin
GEM_PATH=/Users/alex/.rvm/gems/ruby-2.7.1:/Users/alex/.rvm/gems/ruby-2.7.1@global