Ruby: rubygems-update

$ sudo gem update

$ sudo gem install rubygems-update

    Fetching: rubygems-update-2.4.5.gem (100%)
    Successfully installed rubygems-update-2.4.5
    Parsing documentation for rubygems-update-2.4.5
    Installing ri documentation for rubygems-update-2.4.5
    Done installing documentation for rubygems-update after 1 seconds
    1 gem installed

$ sudo update_rubygems
    RubyGems 2.4.5 installed
    Parsing documentation for rubygems-2.4.5
    Installing ri documentation for rubygems-2.4.5

$ sudo gem update