title: JupyterHub JupyterLab - ImportError: cannot import name 'AsyncKernelManager' from 'jupyter_client.manager'
body: <p>I have been running JupyterHub under k8s in notebook mode but want to switch to JupyterLab now. When I launch JupyterLab first I am asked to rebuild the kernel (which fails) so I then rather don't rebuild. Next:</p>
  <p>When I try to launch a python3 kernel, in the logs (JS console and on the container backend) I get:</p>
  <pre><code>ImportError: cannot import name 'AsyncKernelManager' from 'jupyter_client.manager'
  </code></pre>
  <p>If I open a terminal from inside JupyterLab and execute</p>
  <pre><code>python -c &quot;from jupyter_client import AsyncKernelManager&quot;
  </code></pre>
  <p>there is no problem.</p>
  <p>How on earth to proceed?</p>
  <p>PS There is an open github ticket on this here - without much information <a href="https://github.com/jupyter/jupyter_client/issues/551" rel="nofollow noreferrer">https://github.com/jupyter/jupyter_client/issues/551</a></p>