title: flask-wtforms field required
body: <p>how i can add tag required on this flask code :</p>
  
  <pre><code>{{ form.youtube_href(type='url', class='form-control') }}
  </code></pre>
  
  <p>actual output is :</p>
  
  <pre><code>&lt;input class="form-control" id="youtube_href" name="youtube_href" value="" type="url"&gt;
  </code></pre>
  
  <p>need this output bat give error :</p>
  
  <pre><code>&lt;input class="form-control" id="youtube_href" name="youtube_href" value="" type="url" required&gt;
  </code></pre>
  
  <p>im tried this bat give error :</p>
  
  <pre><code>{{ form.youtube_href(type='url', class='form-control', 'required') }}
  </code></pre>