[hooks] fix extra_props handling on python3
The json module expects str, not bytes, so we need to do the decoding.
.. -*- coding: utf-8 -*-
Server Architecture
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.. image:: images/server-class-diagram.png
`Diagramme ArgoUML`_
[FIXME]
Make a downloadable source of zargo file.
.. _`Diagramme ArgoUML`: cubicweb.zargo