python3Packages.zodb: fix compatibility with transaction 3.0
python3Packages.zodb: fix compatibility with transaction 3.0

zodb build broke with the python3Packages.transaction upgrade that
happened in f054f498400b285f0893727a2c039c802d771925.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs