title: Downgrading Ruby Version for my Rails App
body: <p>I'm trying to deploy my app 'project'. It's written in Ruby using Rails and it says I need to downgrade Ruby from 2.5.1 to 2.4.0. I've tried a mix of tinkering with my Gemfile and some RVM commands in my Terminal but nothing seems to work. SOS pls send help!</p>
  
  <p>I changed the ruby v in the Gemfile to "2.4.0" and when I enter the directory it notifies me that:</p>
  
  <pre><code>Using: /Users/me/.rvm/gems/ruby-2.4.0@rails3
  </code></pre>
  
  <p>Then I tried to run "rails s" and receive: </p>
  
  <pre><code>Ignoring nokogiri-1.8.3 because its extensions are not built.  Try: gem pristine nokogiri --version 1.8.3
  /Users/me/.rvm/gems/ruby-2.4.0@rails3/gems/railties-5.2.0/lib/rails/app_loader.rb:53: warning: Insecure world writable dir /usr/local/bin in PATH, mode 040777
  Ignoring bcrypt-3.1.12 because its extensions are not built.  Try: gem pristine bcrypt --version 3.1.12
  Ignoring bindex-0.5.0 because its extensions are not built.  Try: gem pristine bindex --version 0.5.0
  Ignoring bootsnap-1.3.0 because its extensions are not built.  Try: gem pristine bootsnap --version 1.3.0
  Ignoring byebug-10.0.2 because its extensions are not built.  Try: gem pristine byebug --version 10.0.2
  Ignoring ffi-1.9.25 because its extensions are not built.  Try: gem pristine ffi --version 1.9.25
  Ignoring msgpack-1.2.4 because its extensions are not built.  Try: gem pristine msgpack --version 1.2.4
  Ignoring nio4r-2.3.1 because its extensions are not built.  Try: gem pristine nio4r --version 2.3.1
  Ignoring nokogiri-1.8.3 because its extensions are not built.  Try: gem pristine nokogiri --version 1.8.3
  Ignoring puma-3.11.4 because its extensions are not built.  Try: gem pristine puma --version 3.11.4
  Ignoring sqlite3-1.3.13 because its extensions are not built.  Try: gem pristine sqlite3 --version 1.3.13
  Ignoring websocket-driver-0.7.0 because its extensions are not built.  Try: gem pristine websocket-driver --version 0.7.0
  /Users/brianna/.rvm/rubies/ruby-2.4.0/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- bundler (LoadError)
      from /Users/me/.rvm/rubies/ruby-2.4.0/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:55:in `require'
      from /Users/me/proj/bin/spring:8:in `&lt;top (required)&gt;'
      from bin/rails:3:in `load'
      from bin/rails:3:in `&lt;main&gt;'
  </code></pre>