finish yesterday work on rql constraints: * Fix inheritance pb: there are some places where we filter constraints according to the class hierarchy, so rql unique constraint should'nt be neither a RQLContraint nor a RQLVocabularyConstraint subclass. Added test in unittest_schema reflecting this. * So now we have to get explicitly RQLUniqueConstraint where desired (eg in server/hooks.py) * Update i18ncubicweb command to include constraint types in generated pot file (this should have been there for a while...) * Update unittest_schemaserial which has been broken when serializing format for rql constraints has changed

TACHES
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-- écrire objet stocke/manipule les données

-- extraire tests de chaîne de caractère

* utiliser sqlite 

* écrire fonction prend chemin en argument et renvoie contenu

* extraire tests (chaîne de caractère) de spec 

* utiliser yams pour schéma