Test jupyter client

[davidbrochart]

No description provided.

[mriedem]

@davidbrochart I recreated the issue in #1550:

https://travis-ci.org/github/jupyter/nbconvert/jobs/766808690#L1370

self = <nbconvert.preprocessors.execute.ExecutePreprocessor object at 0x7f3e7ca1dd30>

msg_id = '238d6f9e-e6ea4495439b51dfd5175f5b_1'

cell = {'cell_type': 'code', 'metadata': {}, 'outputs': [], 'source': 'from __future__ import print_function\nfrom IPython.display import clear_output'}

timeout = 1

    def _poll_for_reply(self, msg_id, cell=None, timeout=None):

        try:

            # check with timeout if kernel is still alive

            msg = self.kc.shell_channel.get_msg(timeout=timeout)

>           if msg['parent_header'].get('msg_id') == msg_id:

E           TypeError: 'coroutine' object is not subscriptable

[davidbrochart]

Thanks Matt, it is because we should use e.g. self.kc.get_shell_msg() instead of self.kc.shell_channel.get_msg() (see jupyter/jupyter_client#640 (comment)).

[jasongrout]

We are now testing master against jupyter_client 7.0.2: https://github.com/jupyter/nbconvert/runs/3592021910#step:7:35

Please let us know if we need to move forward with different tests of different versions of jupyter_client on master.