import os
import logging
import transaction

from ZODB import FileStorage, DB
from BTrees.OOBTree import OOBTree

NAME = "chow.fs"

logging.basicConfig()

def open():
    global fstorage, db, conn, root
    fstorage = FileStorage.FileStorage(NAME)
    db = DB(fstorage)
    conn = db.open()
    root = conn.root()

def close():
    conn.close()
    db.close()

open()
sv = transaction.savepoint()
root['files'] = OOBTree()
sv.rollback()

if 0:  # if 1, no mysterious errors later
    transaction.abort()
# Something related to savepoints is surviving across the
# close, which causes later problems.
close()

os.unlink(NAME)

open()
root['files'] = OOBTree()
transaction.commit()  # dies here
"""
First an error is logged:

ERROR:txn.1024:Error in tpc_abort() on manager <Connection at 00a26c90>
Traceback (most recent call last):
  File "C:\code\zodb3.5\src\transaction\_transaction.py", line 474, in _cleanup
    rm.tpc_abort(self)
  File "C:\code\zodb3.5\src\ZODB\Connection.py", line 620, in tpc_abort
    self._storage.tpc_abort(transaction)
  File "C:\code\zodb3.5\src\ZODB\BaseStorage.py", line 193, in tpc_abort
    self._abort()
  File "C:\code\zodb3.5\src\ZODB\FileStorage\FileStorage.py", line 939, in _abort
    if self._nextpos:
AttributeError: 'FileStorage' object has no attribute '_nextpos'

Then a code-visible exception occurs;
Traceback (most recent call last):
  File "what.py", line 38, in ?
    transaction.commit()
  File "C:\code\zodb3.5\src\transaction\_manager.py", line 96, in commit
    return self.get().commit(sub, deprecation_wng=False)
  File "C:\code\zodb3.5\src\transaction\_transaction.py", line 393, in commit
    self._saveCommitishError() # This raises!
  File "C:\code\zodb3.5\src\transaction\_transaction.py", line 391, in commit
    self._commitResources()
  File "C:\code\zodb3.5\src\transaction\_transaction.py", line 434, in _commitResources
    rm.tpc_begin(self)
  File "C:\code\zodb3.5\src\ZODB\Connection.py", line 468, in tpc_begin
    self._normal_storage.tpc_begin(transaction)
  File "C:\code\zodb3.5\src\ZODB\BaseStorage.py", line 216, in tpc_begin
    self._clear_temp()
  File "C:\code\zodb3.5\src\ZODB\FileStorage\FileStorage.py", line 851, in _clear_temp
    self._tfile.seek(0)
ValueError: I/O operation on closed file
"""

close()