try:
    sess.add(cat2)
    sess.commit()
except sqlalchemy.exc.IntegrityError, exc:
    reason = exc.message
    if reason.endswith('is not unique'):
            print "%s already exists" % exc.params[0]
            sess.rollback()

apimanager.create_api(
    Model,
    collection_name="models",
    **base_writable_api_settings)