cubicweb #3365511 Correct or document i18ncube behavior [open]

When we apply i18ncube on a cube whose schema EntityType definition classes have docstrings which coincide with the the name of these definition classes (e.g.:

class FooType(EntityType):
    """FooType"""
    ...

), i18ncube crashes.

priorityminor
typebug
done in<not specified>
closed by<not specified>