Traceback (most recent call last):
  File "ez.py", line 330, in ?
    s.expunge(o)
  File "/home/alex/pydev/Sqlalchemy/trunk/sqlalchemy/orm/session.py", line 385, in expunge
    self.uow._remove_deleted(c)
  File "/home/alex/pydev/Sqlalchemy/trunk/sqlalchemy/orm/unitofwork.py", line 112, in _remove_deleted
    del self.identity_map[obj._instance_key]
KeyError: (<class '__main__.SomeClass'>, (48931L, 1L), None)