A small point re: MEP22 API design: having both ToolManager.add_tool and ToolContainerBase.add_tool as user-facing APIs (see e.g. toolmanager_sgskip.py) is slightly awkward, given that they actually have different signatures and do different things.

(I guess one could even ask whether the ToolManager and ToolContainer actually need to exist as separate objects -- a single ToolManager/Container object could e.g. hold the GUI toolbar widget as attribute instead of inheriting from it, for example. This would perhaps also avoid the slight inconsistency that adding a tool to the toolbar needs two calls (add_tool both on the manager and the container), whereas removing it only needs ont (remove_tool on the container); again, see toolmanager_sgskip.py).