Syntax Error when loading gem on Ruby 2.4.x

[vovimayhem]

When starting the app, the following error happens: on Ruby 2.4.5:

/usr/local/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:65:in `require': /usr/local/bundle/gems/on_container-0.0.17/lib/on_container/ops/service_connection_checks.rb:15: syntax error, unexpected keyword_rescue, expecting keyword_end (SyntaxError)
        rescue Errno::ECONNREFUSED
              ^
/usr/local/bundle/gems/on_container-0.0.17/lib/on_container/ops/service_connection_checks.rb:41: syntax error, unexpected keyword_end, expecting end-of-input
        from /usr/local/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:65:in `require'
        from /usr/local/bundle/gems/on_container-0.0.17/lib/on_container/dev/rails.rb:17:in `<top (required)>'
        from /usr/local/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:130:in `require'
        from /usr/local/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:130:in `rescue in require'
        from /usr/local/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:34:in `require'
        from bin/dev-entrypoint:5:in `<main>'