Jupyter installation is using tornado 6 but it not work with tornado 6

[timotta]

When installing jupyter in a new environment, we cannot use the web notebooks because it cannot connect to the kernel. The following message appear on terminal, while in the notebook appears the message "Connecting to kernel" indefinitely.

[I 17:32:35.114 NotebookApp] Adapting to protocol v5.1 for kernel 3a797793-0a5d-4157-a1f1-048486a13d67
/home/tiago.motta/.virtualenvs/teste1/lib/python3.6/site-packages/notebook/base/zmqhandlers.py:284: RuntimeWarning: coroutine 'WebSocketHandler.get' was never awaited
  super(AuthenticatedZMQStreamHandler, self).get(*args, **kwargs)
[W 17:32:36.131 NotebookApp] Replacing stale connection: 3a797793-0a5d-4157-a1f1-048486a13d67:fbd7c223acee449386fcc14885dfa03f

How to reproduce:

$ pip install jupyter
$ pip freeze | grep tornado
tornado==6.0
$ jupyter notebook

Workaround:

pip install tornado==5.1.1

[JohnCrickett]

I see the same issue with Python 3.6.7 on Windows.

[jasongrout]

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

[minrk]

Thanks for tracking these @jasongrout! Closing, since this is fixed in 5.7.5