TypeError: argument of type 'NoneType' is not iterable

[ppanchal-mobiz]

I can run linting locally using python -m flake8 --ignore E128,E302,E305,W292,BLK100 --max-line-length 120 --exclude .venv command without showing up any errors, but my linting GitHub Action suddenly started failing with the following error. Everything was working as expected until a few days ago.

/opt/hostedtoolcache/Python/3.12.0/x64/bin/flake8 --ignore E128,E302,E305,W292,BLK100 --max-line-length 120 backend
multiprocessing.pool.RemoteTraceback: 
"""
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/multiprocessing/pool.py", line 125, in worker
    result = (True, func(*args, **kwds))
                    ^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/site-packages/flake8/checker.py", line 83, in _mp_run
    ).run_checks()
      ^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/site-packages/flake8/checker.py", line 526, in run_checks
    self.run_ast_checks()
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/site-packages/flake8/checker.py", line 428, in run_ast_checks
    for line_number, offset, text, _ in runner:
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/site-packages/bugbear.py", line 61, in run
    if self.should_warn(e.message[:4]):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/site-packages/bugbear.py", line 153, in should_warn
    if code[:i] in self.options.select:
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: argument of type 'NoneType' is not iterable
"""

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

Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.12.0/x64/bin/flake8", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/site-packages/flake8/main/cli.py", line 23, in main
    app.run(argv)
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/site-packages/flake8/main/application.py", line 198, in run
    self._run(argv)
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/site-packages/flake8/main/application.py", line 187, in _run
    self.run_checks()
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/site-packages/flake8/main/application.py", line 103, in run_checks
    self.file_checker_manager.run()
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/site-packages/flake8/checker.py", line 236, in run
    self.run_parallel()
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/site-packages/flake8/checker.py", line 205, in run_parallel
    self.results = list(pool.imap_unordered(_mp_run, self.filenames))
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/multiprocessing/pool.py", line 873, in next
    raise value
TypeError: argument of type 'NoneType' is not iterable
Error: The process '/opt/hostedtoolcache/Python/3.12.0/x64/bin/flake8' failed with exit code 1

Snippet of the workflow file:

- name: Flake8 linting
          uses: py-actions/flake8@v2
          with:
            ignore: "E128,E302,E305,W292,BLK100"
            max-line-length: 120
            path: ${{ env.AZURE_WEBAPP_PACKAGE_PATH }}
            plugins: "flake8-bugbear==22.1.11 flake8-black"

[Enitoxy]

Same exact error happening, I hope there's a fix soon

[ppanchal-mobiz]

Following up as we are still facing the issue. Thank you.

[zjordan-zhang]

Had similar issue, changing Python version to be <= 3.10 seems to work for me.