title: could not open extension control file for Citext in postgresql 10
body: <p>I just installed postgresql 10 in Fedora 28. then I did a mix ecto.migrate but it says</p>
  
  <blockquote>
    <p>** (Postgrex.Error) ERROR 58P01 (undefined_file): could not open extension control file "/usr/pgsql-10/share/extension/citext.control":
    No such file or directory</p>
  </blockquote>
  
  <p>I installed postgresql10-contrib also..</p>
  
  <p>pg_config --sharedir
  returns </p>
  
  <pre><code>/usr/share/pgsql
  </code></pre>
  
  <p>and I can find </p>
  
  <pre><code>/usr/share/pgsql/extension/citext.control
  </code></pre>
  
  <p>file.
  but not in /usr/pgsql-10/share/extension directory.</p>
  
  <p>what am I missing?</p>