Browsing French translation

1697.

Twisted provides a mechanism called <code class="API" base="twisted.persisted.styles">Versioned</code> to ease these upgrades. Each version of the data structure (i.e. each version of the class) gets a version number. This number must change every time you add or remove a data attribute to the class. It must also change every time you modify one of those data attributes: for example, if you use a string in one version and an integer in another, those versions must have different version numbers.