thread.local does not work with yielding code

[Angus Salkeld]

Heat uses yield to explicitly give up control and do other processing see:
https://github.com/openstack/heat/blob/master/heat/engine/scheduler.py
https://github.com/openstack/heat/blob/master/heat/engine/stack.py#L572

This is quite similar to how tulip/asyncio works.

What would be awesome is an api where we can control the switching of the thread.local.

This could be a start for ideas:
https://github.com/vkryachko/tasklocals/blob/master/tasklocals/__init__.py

So when you call: https://github.com/stackforge/osprofiler/blob/master/osprofiler/profiler.py#L33
we could provide a "different" thread.local wrapper.