title: Ignoring gems because its extensions are not built
body: <p>I installed the rails in my machine</p>
  
  <p>ruby 2.3.1</p>
  
  <p>rails 5.1.4</p>
  
  <p>Ubuntu 16.04 os</p>
  
  <p>After rails installation, When i check rails version <code>rails -v</code>
  It throws Ignoring "Some gems list" because its extensions are not built</p>
  
  <pre><code>Ignoring nokogiri-1.8.1 because its extensions are not built.  Try: gem pristine nokogiri --version 1.8.1
  Ignoring bindex-0.5.0 because its extensions are not built.  Try: gem pristine bindex --version 0.5.0
  Ignoring byebug-9.1.0 because its extensions are not built.  Try: gem pristine byebug --version 9.1.0
  Ignoring curb-0.9.4 because its extensions are not built.  Try: gem pristine curb --version 0.9.4
  Ignoring executable-hooks-1.3.2 because its extensions are not built.  Try: gem pristine executable-hooks --version 1.3.2
  Ignoring ffi-1.9.18 because its extensions are not built.  Try: gem pristine ffi --version 1.9.18
  Ignoring gem-wrappers-1.3.2 because its extensions are not built.  Try: gem pristine gem-wrappers --version 1.3.2
  Ignoring gem-wrappers-1.2.7 because its extensions are not built.  Try: gem pristine gem-wrappers --version 1.2.7
  Ignoring nio4r-2.2.0 because its extensions are not built.  Try: gem pristine nio4r --version 2.2.0
  Ignoring pg-0.21.0 because its extensions are not built.  Try: gem pristine pg --version 0.21.0
  Ignoring websocket-driver-0.6.5 because its extensions are not built.  Try: gem pristine websocket-driver --version 0.6.5
  Rails 5.1.4
  </code></pre>
  
  <p>After new rails application created successfully
  When i run <code>bundle install</code> 
  It throws errror message like:</p>
  
  <pre><code>An error occurred while installing json (1.8.6), and Bundler cannot continue.
  Make sure that `gem install json -v '1.8.6'` succeeds before bundling.
  </code></pre>