title: pg_ext.so: undefined symbol: rb_thread_select
body: <pre><code>bash-4.2# rake db:create
  /opt/rubystack-2.3.1-0/ruby/bin/.ruby.bin: symbol lookup error: /opt/rubystack-2.3.1-0/ruby/lib/ruby/gems/2.3.0/gems/pg-0.18.4/lib/pg_ext.so: undefined symbol: rb_thread_select
  bash-4.2# ruby -v
  ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-linux]
  bash-4.2# rails -v
  Rails 4.2.6
  bash-4.2# gem list pg
  
  *** LOCAL GEMS ***
  
  
  
    pg (0.18.4, 0.15.1)
  </code></pre>
  
  <p>what's the problem?  it's bitnami's ruby stack.</p>
  
  <p><strong>NOTE:</strong> It's NOT pg version's bug? Please check my log! <strong>Ruby version 2.3.1, <code>pg</code> version 0.18.4.</strong></p>