Get Cancelled Task State Futures.

[BarrySlyDelgado]

We have some use cases in which we want to check if a task is cancelled (FuturesExecutor). When a task is cancelled, this state may become an attribute of the task and should be retrievable via the Python bindings.

• Cancel tasks correctly via futures executor.
• Retrieve cancelled status.

This is the current code that does not work:

cctools/taskvine/src/bindings/python3/ndcctools/taskvine/futures.py

Lines 239 to 248 in 034aba1

	def cancel(self):
	self._task._module_manager.cancel_by_task_id(self._task.id)
	self._state = CANCELLED
	def cancelled(self):
	state = self._task._module_manager.task_state(self._task.id)
	if state == cvine.VINE_TASK_CANCELED:
	return True
	else:
	return False