Server can't start for some users, ImportError: The Jupyter Server requires tornado >=6.1.0

[limotkl]

Bug description

Only one user can't start notebook server, the pod keep crashloopbackoff, and finally get timeout in jhublab. Works fine for other users.

Error message from log:

Traceback (most recent call last):
  File "/opt/conda/lib/python3.8/site-packages/jupyter_server/serverapp.py", line 50, in <module>
    assert tornado.version_info >= MIN_TORNADO
AssertionError

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/opt/conda/bin/jupyter-labhub", line 6, in <module>
    from jupyterlab.labhubapp import main
  File "/opt/conda/lib/python3.8/site-packages/jupyterlab/__init__.py", line 7, in <module>
    from .labapp import LabApp
  File "/opt/conda/lib/python3.8/site-packages/jupyterlab/labapp.py", line 15, in <module>
    from jupyterlab_server import slugify, WORKSPACE_EXTENSION
  File "/opt/conda/lib/python3.8/site-packages/jupyterlab_server/__init__.py", line 4, in <module>
    from .app import LabServerApp
  File "/opt/conda/lib/python3.8/site-packages/jupyterlab_server/app.py", line 7, in <module>
    from jupyter_server.extension.application import ExtensionApp, ExtensionAppJinjaMixin
  File "/opt/conda/lib/python3.8/site-packages/jupyter_server/extension/application.py", line 20, in <module>
    from jupyter_server.serverapp import ServerApp
  File "/opt/conda/lib/python3.8/site-packages/jupyter_server/serverapp.py", line 52, in <module>
    raise ImportError(_i18n("The Jupyter Server requires tornado >=%s.%s.%s") % MIN_TORNADO) from e
ImportError: The Jupyter Server requires tornado >=6.1.0 

Expected behaviour

it should start a new server for user

Actual behaviour

Pod keep crashloopbackoff and get timeout error in jhublab

How to reproduce

1. Log in to jhub
2. Select one profile
3. Start new server

Your personal set up

My personal set up should be fine cause in our project this issue happens for only one user, works fine for others.

• Version(s): appVersion: 1.3.0 helmVersion: 0.11.1

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[consideRatio]

Closed as duplicated of https://github.com/jupyterhub/zero-to-jupyterhub-k8s/issues/2430#event-5429714243