[This commit](https://github.com/jupyter/jupyter_client/commit/f365a22a22591c3bae04723b804585fe11934ce5) in jupyter-client 7 removes the `block` kwarg for `get_msg` used [here](https://github.com/jupyter/kernel_gateway/blob/213a8179c5a6e81a301cafc467549ef90855468f/kernel_gateway/services/kernels/manager.py#L104)
