title: Unpacking the update... Could not create directory. Wordpress
body: <p>When I instal <code>nextgen-gallery</code> plugins. This error message appears </p>
  
  <pre><code>Downloading update from https://downloads.wordpress.org/plugin/nextgen-gallery.zip…
  
  Unpacking the update…
  
  Could not create directory.
  </code></pre>
  
  <p>How can I fix this problem ?</p>