Cycler object has no attribute 'next' in Python 3.4.3

Python 3.4.3, Pyramid 1.5.7, Jinja 2.8 (2.7.3 produce the same error)

I got a weird exception

jinja2.exceptions.UndefinedError: 'jinja2.utils.Cycler object' has no attribute 'next'

in string

<li class='struct-item{{ row.next() }}' data-id="{{ category._id }}" 
data-owner="{{ category.owner }}">

template:

<ul>
{% set row = cycler('', ' back') %}
{% for category in categories[0] recursive %}
    <li class='struct-item{{ row.next() }}' data-id="{{ category._id }}" 
    data-owner="{{ category.owner }}">
        <div class="title">{{ category.caption }}</div>
        <div class="action">
            {% if not loop.depth0 %}
            <a href='#' class="category-add">
                <img src='/static/admin/img/action-add.png'>
             </a>
             {% endif %}
            <a href='#' class="category-edit">
                <img src='/static/admin/img/action-edit.png'>
            </a>
            <a href='#' class="category-delete">
                <img src='/static/admin/img/action-delete.png'>
            </a>
        </div>
    </li>
    {% if category._id in categories %}
        <ul class="children">{{ loop(categories[category._id]) }}</ul>
    {% endif %}
{% endfor %}
</ul>

When I make a call print(dir(self)) in a constructor Cycler, echo was

['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', 
 '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', 
 '__module__', '__ne__', '__new__', '__next__', '__reduce__', '__reduce_ex__', 
 '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 
 'current', 'items', 'pos', 'reset']

that means Cycler object really has no next method. Temporary fix is jinja2.utils.Cycler.next = jinja2.utils.Cycler.__next__ in a Pyramidmain method, but…

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Hey guys. This issue has been opened more than month ago.

This can be fixed by adding almost the same function implements_iterator in code block if not PY2 in _compat.py.

    def implements_iterator(cls):
        cls.next = cls.__next__
        return cls

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And I’m very sorry, I was wrong. In Python 2.7.3 current release works fine, as expected.