Recent jupyterhub servers crash with error from jinja2 version 3.1.0

[valerioa]

Recent jupyterhub servers crash with this error from jinja2

    Traceback (most recent call last):
      File "/opt/conda/lib/python3.9/site-packages/tornado/web.py", line 1704, in _execute
        result = await result
      File "/opt/conda/lib/python3.9/site-packages/tornado/gen.py", line 775, in run
        yielded = self.gen.send(value)
      File "/opt/conda/lib/python3.9/site-packages/notebook/notebook/handlers.py", line 95, in get
        self.write(self.render_template('notebook.html',
      File "/opt/conda/lib/python3.9/site-packages/notebook/base/handlers.py", line 516, in render_template
        return template.render(**ns)
      File "/opt/conda/lib/python3.9/site-packages/jinja2/environment.py", line 1291, in render
        self.environment.handle_exception()
      File "/opt/conda/lib/python3.9/site-packages/jinja2/environment.py", line 926, in handle_exception
        raise rewrite_traceback_stack(source=source)
      File "/opt/conda/lib/python3.9/site-packages/notebook/templates/notebook.html", line 1, in top-level template code
        {% extends "page.html" %}
      File "<template>", line 2, in top-level template code
      File "/opt/conda/lib/python3.9/site-packages/notebook/templates/page.html", line 154, in top-level template code
        {% block header %}
      File "/opt/conda/lib/python3.9/site-packages/notebook/templates/notebook.html", line 115, in block 'header'
        {% for exporter in get_frontend_exporters() %}
      File "/opt/conda/lib/python3.9/site-packages/notebook/notebook/handlers.py", line 23, in get_frontend_exporters
        from nbconvert.exporters.base import get_export_names, get_exporter
      File "/opt/conda/lib/python3.9/site-packages/nbconvert/__init__.py", line 4, in <module>
        from .exporters import *
      File "/opt/conda/lib/python3.9/site-packages/nbconvert/exporters/__init__.py", line 3, in <module>
        from .html import HTMLExporter
      File "/opt/conda/lib/python3.9/site-packages/nbconvert/exporters/html.py", line 14, in <module>
        from jinja2 import contextfilter
    ImportError: cannot import name 'contextfilter' from 'jinja2' (/opt/conda/lib/python3.9/site-packages/jinja2/__init__.py)

Describe how to replicate the bug.
Install and run latersversion of jupyterhub

Describe the expected behavior that should have happened but didn't.
jupyterhub should not e crashing,.

Environment:

• Python version: Python 3.7.10
• Jinja version: 3.1.0

[davidism]

Duplicate of #1626

[davidism]

Actually, better duplicate is the actual report in nbconvert, which your traceback points to.

• HTML exporter DeprecationWarning: 'jinja2.Markup' is deprecated and will be removed in Jinja 3.1 jupyter/nbconvert#1605
• [BUG] module 'jinja2.utils' has no attribute 'escape' jupyter/nbconvert#1736
• Import Markup and escape directly from MarkupsSafe jupyter/nbconvert#1737