transaction: add releasefn to notify the end of a transaction scope...
transaction: add releasefn to notify the end of a transaction scope
'releasefn' is used by subsequent patch, to do appropriate action
according to the result of it at the end of a transaction scope.
To ensure that 'releasefn' is invoked only once, this patch invokes it
after assignment 'self.journal = None', because such assignment
prevents from invoked 'transaction._abort()' again via '__del__()'.
def __del__(self):
if self.journal:
self._abort()
