Selectively display Postach.io tags not in a list called skiptags

gistfile1.py

{% if post.tags %}
  <ul class="post-tags">
    {% for tag in post.tags %}
      {% if tag not in skiptags %}
        <li><a href="/tag/{{ tag }}">{{ tag }}</a></li>
      {% endif %}
    {% endfor %}
  </ul>
{% endif %}