Restore usage of flake8 and add to CI · jupyter/nbclassic@ef317da

Run Test: opt/hostedtoolcache/Python/3.12.8/x64/lib/python3.12/site-packages/traitlets/traitlets.py#L1897

ServerApp.token config is deprecated in jupyter-server 2.0. Use IdentityProvider.token

Run Test: opt/hostedtoolcache/Python/3.12.8/x64/lib/python3.12/site-packages/jupyter_server/serverapp.py#L2813

The synchronous ContentsManager classes are deprecated and will not be supported in Jupyter Server 3.0

Run Test: opt/hostedtoolcache/Python/3.12.8/x64/lib/python3.12/site-packages/traitlets/traitlets.py#L1897

ServerApp.token config is deprecated in jupyter-server 2.0. Use IdentityProvider.token

Run Test: opt/hostedtoolcache/Python/3.12.8/x64/lib/python3.12/site-packages/traitlets/traitlets.py#L1897

ServerApp.token config is deprecated in jupyter-server 2.0. Use IdentityProvider.token

Run Test: opt/hostedtoolcache/Python/3.12.8/x64/lib/python3.12/site-packages/jupyter_server/serverapp.py#L2813

The synchronous ContentsManager classes are deprecated and will not be supported in Jupyter Server 3.0

Run Test: opt/hostedtoolcache/Python/3.12.8/x64/lib/python3.12/site-packages/traitlets/traitlets.py#L1897

ServerApp.token config is deprecated in jupyter-server 2.0. Use IdentityProvider.token

Run Test: opt/hostedtoolcache/Python/3.12.8/x64/lib/python3.12/site-packages/traitlets/traitlets.py#L1897

ServerApp.token config is deprecated in jupyter-server 2.0. Use IdentityProvider.token

Run Test: opt/hostedtoolcache/Python/3.12.8/x64/lib/python3.12/site-packages/jupyter_server/serverapp.py#L2813

The synchronous ContentsManager classes are deprecated and will not be supported in Jupyter Server 3.0

Run Test: opt/hostedtoolcache/Python/3.12.8/x64/lib/python3.12/site-packages/traitlets/traitlets.py#L1897

ServerApp.token config is deprecated in jupyter-server 2.0. Use IdentityProvider.token

Run Test: opt/hostedtoolcache/Python/3.12.8/x64/lib/python3.12/site-packages/traitlets/traitlets.py#L1897

ServerApp.token config is deprecated in jupyter-server 2.0. Use IdentityProvider.token

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