fix attributes in derivation by restriction
Brought to you by:
pabigot
The content model is such that restricting elements just works (though the accessors for the inaccessible ones probably should be hidden). Parent type attributes, on the other hand, are overridden when they should be inherited.
Delayed to next beta.
Fixed in [1584]. Turns out I also misunderstood restriction of attributes: unlike elements (which must be explicitly listed if they are to be present in the restriction), unlisted attributes are inherited from the base class, unless they are redefined. They are "removed" by being redefined with use="prohibited". (PyXB did this, excepting this DR, but I thought it was wrong to do so: it's not.)
PyXB now re-uses the map from the parent use when initializing the restricted AttributeUse instance.