src/vs/workbench/contrib/tasks/browser/taskService.ts/TaskService/_getTaskSystem
class TaskService:	protected _getTaskSystem(): ITaskSystem {
		if (this._taskSystem) {
			return this._taskSystem;
		}
		if (this.executionEngine !== ExecutionEngine.Terminal) {
			throw new Error(TaskService.ProcessTaskSystemSupportMessage);
		}
		this._taskSystem = this._createTerminalTaskSystem();
		this._taskSystemListeners =
			[
				this._taskSystem.onDidStateChange((event) => {
					this._taskRunningState.set(this._taskSystem!.isActiveSync());
					this._onDidStateChange.fire(event);
				}),
			];
		return this._taskSystem;
	}