jupyterhub/tests/test_singleuser.py::test_singleuser_app_class[notebook.notebookapp.NotebookApp] fails with dev traitlets

[manics]

Bug description

jupyterhub/tests/test_singleuser.py::test_singleuser_app_class[notebook.notebookapp.NotebookApp] fails when dev traitlets are installed

Expected behaviour

JupyterHub CI tests should pass

Actual behaviour

When https://github.com/ipython/traitlets/tree/0505aef059b03bc93638533af9933004ffe23074 is installed in the Python 3.11 main_dependencies test:

jupyterhub/.github/workflows/test.yml

Lines 166 to 168 in 6502b50

	if [ "${{ matrix.main_dependencies }}" != "" ]; then
	pip install git+https://github.com/ipython/traitlets#egg=traitlets --force
	pip install --upgrade --pre sqlalchemy

One test fails, due to:

$ JUPYTERHUB_SINGLEUSER_APP=notebook.notebookapp.NotebookApp python -m jupyterhub.singleuser --help-all

Traceback (most recent call last):
  File "/test/mambaforge/envs/py11/lib/python3.11/site-packages/notebook/traittypes.py", line 235, in _resolve_classes
    klass = self._resolve_string(klass)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/test/mambaforge/envs/py11/lib/python3.11/site-packages/traitlets/traitlets.py", line 1953, in _resolve_string
    return import_item(string)
           ^^^^^^^^^^^^^^^^^^^
  File "/test/mambaforge/envs/py11/lib/python3.11/site-packages/traitlets/utils/importstring.py", line 30, in import_item
    module = __import__(package, fromlist=[obj])
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ModuleNotFoundError: No module named 'jupyter_server.contents'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<frozen runpy>", line 189, in _run_module_as_main
  File "<frozen runpy>", line 148, in _get_module_details
  File "<frozen runpy>", line 112, in _get_module_details
  File "/test/work/jupyter/jupyterhub/jupyterhub/singleuser/__init__.py", line 67, in <module>
    from .app import SingleUserNotebookApp, main
  File "/test/work/jupyter/jupyterhub/jupyterhub/singleuser/app.py", line 51, in <module>
    SingleUserNotebookApp = make_singleuser_app(App)
                            ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/test/work/jupyter/jupyterhub/jupyterhub/singleuser/mixins.py", line 904, in make_singleuser_app
    empty_parent_app = App()
                       ^^^^^
  File "/test/mambaforge/envs/py11/lib/python3.11/site-packages/traitlets/traitlets.py", line 1239, in __new__
    inst.setup_instance(*args, **kwargs)
  File "/test/mambaforge/envs/py11/lib/python3.11/site-packages/traitlets/traitlets.py", line 1282, in setup_instance
    super(HasTraits, self).setup_instance(*args, **kwargs)
  File "/test/mambaforge/envs/py11/lib/python3.11/site-packages/traitlets/traitlets.py", line 1258, in setup_instance
    init(self)
  File "/test/mambaforge/envs/py11/lib/python3.11/site-packages/notebook/traittypes.py", line 226, in instance_init
    self._resolve_classes()
  File "/test/mambaforge/envs/py11/lib/python3.11/site-packages/notebook/traittypes.py", line 238, in _resolve_classes
    warn(f"{klass} is not importable. Is it installed?", ImportWarning)
TypeError: warn() missing 1 required keyword-only argument: 'stacklevel'

https://github.com/ipython/traitlets/blob/0505aef059b03bc93638533af9933004ffe23074/traitlets/utils/warnings.py#L6-L11
requires a stacklevel kwarg but
https://github.com/jupyter/notebook/blob/v6.5.4/notebook/traittypes.py#L238
doesn't pass it

[manics]

@blink1073 Is this breakage due to ipython/traitlets#838 intended?

[blink1073]

traitlets.warn was never a part of the public API (it wasn't part of _all_). The bug here is that notebook.traittypes is importing warn from traitlets instead of warnings.

[I-Am-D-B]

Did this bug somehow get re-introduced? I'm getting essentially the same thing with 6.5.5, when I didn't yesterday, it looks like.

Traceback (most recent call last):
  File ".......venv/lib/python3.10/site-packages/notebook/traittypes.py", line 235, in _resolve_classes
    klass = self._resolve_string(klass)
  File ".......venv/lib/python3.10/site-packages/traitlets/traitlets.py", line 2009, in _resolve_string
    return import_item(string)
  File ".......venv/lib/python3.10/site-packages/traitlets/utils/importstring.py", line 30, in import_item
    module = __import__(package, fromlist=[obj])
ModuleNotFoundError: No module named 'jupyter_server.contents'

rm -rf venv/
python3.10 -m venv venv
source venv/bin/activate
pip install --force-reinstall -v "notebook>=6,<7"
jupyter-notebook 

Effectively, this worked yesterday, jupyter-notebook 6.5.5 failing to start notebook server today. Only relevant thing I found. Did some underlying dependency that's not pinned for 6.5.5 change?

[minrk]

@I-Am-D-B I don't think that's related. I think you're hitting jupyter/notebook#7048 which is a bug in notebook, but also a backward-incompatible change in traitlets 5.10 that may want reverting. Pinning traitlets<5.10 should fix it for now.

[minrk]

Closing in favor of the jupyter/notebook issue.

[I-Am-D-B]

Thanks @minrk. I did:

pip install --force-reinstall -v "traitlets<5.10" and now jupyter-notebook runs.

Back to what I was trying to actually debug 2 days ago...

[mahmoudsamhoud]

Thanks @minrk
pip install --force-reinstall -v "traitlets<5.10" works just fine