[ZODB-Dev] zc.demostorage2 assumes too much?

[Wolfgang Schnerring]

Hello,

zc.demostorage2 assumes that the tpc_begin() of its underlying
storages takes three parameters (transaction, tid, status), while both
MappingStorage and IStorage only know about the first two.

This strikes me as risky, and it does indeed break, for example when
trying to use a DemoStorage as the 'changes' backend of a
DemoStorage2.

I've tried and removed the status parameter from zc.demostorage2 and
its tests still pass, but I must confess I have no clue what this
status parameter actually does, so I don't really know what (if
anything) to do about this issue.

Thanks for your help,
Wolfgang