I found an alternative way of doing what I wanted to do:
In my python code I create a dict with the data to create the select then I do this:
<span class="input-group-addon">relocate to</span>
<select name="relocate_to" id="relocate_to" multiple="" class="form-control">
{% for k, v in relocate_list.iteritems() %} <!-- relocate_list was a list, is now a dictionary -->
{% if k in context.relocate_to %}
<option value="{{ k }}" selected="">{{ v }}</option>
{% else %}
<option value="{{ k }}">{{ v }}</option>
{% endif %}
{% endfor %}
</select>
I hope this can help someone in the future.
Then I just initialize select2:
$("#relocate_to").select2({
maximumSelectionSize : 9
});