Fixed bug in form_errors template

When the close button is inside a form and the enter key is pressed, then the submit event of the form is released.

For example:
<form action="" method="post">
  <div class="alert alert-danger alert-dismissable alert-link">
    <button class="close" type="button" data-dismiss="alert" aria-hidden="true">&#215;</button>
    {% for error in errors %}
      {{ error }}{% if not forloop.last %}<br>{% endif %}
    {% endfor %}
  </div>
  <input type="text" required="required" name="login" id="id_login" class="form-control">
  <button>Submit</button>
</form>