Update the_controller.rst

[aykin]

The sample code does not work due to an array o string conversion exception. The documentation needs to be updated to reflect the change

[wouterj]

What do you think of updating this with:

{% for flashMessage in app.session.flashbag.get('notice') %}
    <div class="flash-notice">
        {{ flashMessage }}
    </div>
{% endfor %}

(which is the example shown in the book)

[stof]

much better. The code suggested by @aykin would break when there is no notice message

[aykin]

I agree. Though I think it might be a bit too heavy for this section of the document. Perhaps an bare unordered list (without a style class) would be more suitable?

[wouterj]

I think the example isn't that heavy. An unordered list (while being more semantic) would require even more loc :)

[javiereguiluz]

I'm finishing this PR in #5431.

@aykin don't worry about not having finished your PR. This happens sometimes. I've taken your work and finished it in another PR. I've also reused all your original commits so you get full credit for your work. Thanks.