Adding class to main menu based on whether or not a post has a certain tag

gistfile1.txt

{% assign focus = site.pages.news.taxonomy.tags.focus-magazine %}

<li>
    <a href="{{focus.url}}"
        {% if url == focus.url %}class="is-selected"
        {% elsif taxonomy.tags.all contains "focus-magazine" %}class="is-selected"
        {% endif %}>
        {{focus}}
    </a>
</li>

{% assign flag = "false" %}
{% for tagset in site.pages.news.taxonomy %}
    {% for tag in tagset %}
        {% if tag.value == "focus-magazine" %}
            {% assign flag = "true" %}
        {% endif %}
    {% endfor %}
{% endfor %}

<li>
    <a href="{{focus.url}}"
        {% if url == focus.url %}class="is-selected"
        {% elsif type == "post" and parent.slug == news.slug and flag != "true" %}class="is-selected"
        {% endif %}>
        {{focus}}
    </a>
</li>