has()/any() + joined inh, can't pull needed columns out of aliases when things get crazy

need to adapt this down to be simpler, and also compare to what a non joined inh model would do:
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()


engine = create_engine('sqlite:///:memory:', echo = True)

class Location(Base):
   Id = Column( Integer, primary_key =True, autoincrement = True)
   objectType = Column( String(128),nullable = False)
   __tablename__ = 'Location'
   __mapper_args__ = {'polymorphic_on': objectType,'polymorphic_identity': __tablename__}
   name = Column( String(128), nullable =False)

class District(Location):
   Id = Column(Integer,ForeignKey(Location.Id), primary_key = True)
   __tablename__ = 'District'
   __mapper_args__ = {'inherit_condition': Id == Location.Id,'polymorphic_identity': __tablename__}

class Commune(Location):
   Id = Column(Integer,ForeignKey(Location.Id), primary_key = True)
   __tablename__ = 'Commune'
   __mapper_args__ = {'inherit_condition': Id == Location.Id,'polymorphic_identity': __tablename__}
   districtId = Column(Integer,ForeignKey(District.Id))
   district = relation(District, primaryjoin =districtId == District.Id)

class Locality(Location):
   Id = Column(Integer,ForeignKey(Location.Id), primary_key = True)
   __tablename__ = 'Locality'
   __mapper_args__ = {'inherit_condition': Id == Location.Id,'polymorphic_identity': __tablename__}
   communeId = Column(Integer,ForeignKey(Commune.Id))
   commune = relation(Commune, primaryjoin = communeId== Commune.Id)

Base.metadata.create_all(engine)

# I want all localities which are in a district called Foo

s = Session(engine)

#q = s.query(Locality).filter(Locality.commune.has(name='Foo'))

q = s.query(Locality).filter(
    Locality.commune.has(
#        (Locality.name =='foo') 
        Commune.district.has(District.name=='foo')
    )
)

q.all()

#print s.query(Locality).filter(Locality.coohas(
#    Commune.district.has(Commune.name=="foo")
#))
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