title: taxonomy_exists always return false even the taxonomie exist
body: <p>Wordpress function <code>taxonomy_exists</code> that verifies the existence of taxonomy always returns false.</p>
  
  <pre><code> $tax = taxonomy_exists('categorie-video');
   error_log('verify the existence of taxonomy = ' . json_encode($tax));
  </code></pre>
  
  <p>I used <code>Simple Taxonomy</code> plugin to create the taxonomy.</p>