Integrate itota's experimental code: https://github.com/trac-hacks/trac-subtickets-plugin/commit/ae2e9d5320eaba75da1619d180e6f9c9b46901a91 This will also handle https://github.com/roandbox/trac-subtickets-plugin/commit/9afe5e48c0ab5de34bd4a27adedc69bf7b2431cc
