Demonstrates how an `InvalidRequestError` is raised where it shouldn't be.

session.py

from sqlalchemy import orm
from sqlalchemy.engine import create_engine
from sqlalchemy.ext.declarative.api import declarative_base
from sqlalchemy.orm.scoping import scoped_session
from sqlalchemy.orm.session import sessionmaker
from sqlalchemy.schema import Column
from sqlalchemy.types import String
from zope.sqlalchemy.datamanager import ZopeTransactionExtension
import binascii
import os
import transaction


DBSession = scoped_session(sessionmaker())


Base = declarative_base()


class Session(Base):
    __tablename__ = 'session'
    id = Column(String, primary_key=True)

    def __init__(self):
        self.id = binascii.hexlify(os.urandom(32))


class ObjectFactory(dict):

    def __init__(self):
        self.session = Session()
        self.db_session = DBSession()
        self.db_session.add(self.session)


def test_invalid_request_error():
    engine = create_engine('sqlite://')
    DBSession.configure(bind=engine)
    Base.metadata.create_all(engine)
    db_session = DBSession()
    sess = Session()
    db_session.add(sess)
    session = ObjectFactory()
    assert db_session is session.db_session
    assert db_session is \
        orm.session.Session.object_session(session.session)
    assert session.session in db_session
    assert isinstance(session.session, Session)
    assert isinstance(Session.id, orm.attributes.InstrumentedAttribute)
    db_session.expire(session.session)
    db_session.expunge(session.session)
    transaction.commit()
    db_session.close()

if __name__ == '__main__':
    test_invalid_request_error()