Jupyter Notebook never becomes ready to execute cell

[dallasssimpson]

Starting today 3/1/2018 I started receiving the following error in the logs generated by /bin/bash -c jupyter lab &> /tmp/jupyterlab.

I found:
Exception in callback <bound method WebSocketMixin.send_ ping of <notebook.terminal.handlers.TermSocket object at 0x7f5d24576668>> Traceback (most recent call last): File "/usr/local/lib/python3.5/dist-packages/tornado/ioloop.py", line 907, in _run return self.callback() File "/usr/local/lib/python3.5/dist-packages/notebook/base/zmqhandlers.py" , line 175, in send_ping if self.stream.closed() and self.ping_callback is not None: AttributeError: 'NoneType' object has no attribute 'closed'

Tornado released a new version today that seems to break things.

Downgrading Tornado from 6.0 to 5.1.1 and restarting Jupyter seems to resolve the issue.

[audy]

Same. This appears to fix it but it has not been released yet. Tag?

[davesque]

Same issue.

[C0NTRIBUTE]

Same issue.

[jasongrout]

See also #4399 for tornado 6 issues.

[dazzag24]

Same issue here. Both jupyter-lab and notebook were broken until I downgraded tornado from 6.0.0. to 5.1.1

[jasongrout]

My guess is this is the incompatibility with tornado 6 a lot of people have been experiencing. See #4439 and #4449. The solution would be either upgrading notebook to version 5.7.5, or downgrading tornado to version 5.1.1.

[minrk]

Yup, this is fixed in notebook 5.7.5