[ZODB-Dev] [zodb4] calling get_transaction().abort() dies

[Ury Marshak]

A simple attempt to call get_transaction().abort() fails with the following:

Traceback (most recent call last):
  File "C:\WORk\test\tst.py", line 16, in ?
    get_transaction().abort()
  File "C:\Python22\Lib\site-packages\Transaction\Transaction.py", line 49,
in abort
    self._manager.abort(self)
  File "C:\Python22\Lib\site-packages\Transaction\Manager.py", line 82, in
abort
    super(ThreadedTransactionManager, self).abort(txn)
  File "C:\Python22\Lib\site-packages\Transaction\Manager.py", line 40, in
abort
    r.abort(txn)
  File "C:\Python22\Lib\site-packages\ZODB\Connection.py", line 497, in
abort
    self._cache.invalidateMany(self._modified)
AttributeError: Connection instance has no attribute '_modified'

Wrong usage? If so, how can I abort the transaction and throw away all the
changes?
Sample code:

from ZEO import ClientStorage
from ZODB.DB import DB
import Persistence
from ZODB import FileStorage
from Transaction import get_transaction

if __name__=='__main__':
    #
    storage = FileStorage.FileStorage('ffff')
    db = DB( storage )
    conn = db.open()
    root = conn.root()
    root[1] = 1
    get_transaction().abort()

OSes - win 2000, winXP, ZODB4 - current CVS, python 2.2.1

Ury