Foxy issue

• Exception never retrieved when using MultiThreadedExecutor and Timers

  • https://github.com/ros2/rclpy/issues/983
  • https://github.com/ros2/rclpy/issues/1016
  • https://github.com/ros2/rclpy/pull/1017

• Cancelling asynchronous tasks / Future has no effect

  • https://github.com/ros2/rclpy/issues/1099
  • https://github.com/ros2/rclpy/issues/1098
  • https://github.com/ros2/rclpy/pull/971