Fix torchscript related test failures. Fix flake8.

[pearu]

As in title. An alternative to #4061.

Motivation: having working unit-tests is a prerequisite for transition to torch stable ABI per #3902 .

PLEASE NOTE THAT THE TORCHAUDIO REPOSITORY IS NO LONGER ACTIVELY MONITORED. You may not get a response. For open discussions, visit https://discuss.pytorch.org/.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/audio/4069

• 📄 Preview Python docs built from this PR

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❗ 1 Active SEVs

There are 1 currently active SEVs. If your PR is affected, please view them below:

• ROCm CI/CD workflows failing due to : download from https://api.github.com/repos/pytorch/pytorch timed out.

❌ 8 New Failures, 1 Unrelated Failure

As of commit 4763982 with merge base 1c66402 ():

NEW FAILURES - The following jobs have failed:

• .github/workflows/bandit.yml (gh)
• .github/workflows/integration-test.yml (gh)
• .github/workflows/lint.yml (gh)
• .github/workflows/pr-labels.yml (gh)
• .github/workflows/unittest-macos-cpu.yml (gh)
• .github/workflows/unittest-windows-cpu.yml (gh)
• .github/workflows/unittest-windows-gpu.yml (gh)
• Build Windows Wheels / pytorch/audio / upload / upload-wheel-py3_10-xpu (gh)
  Unable to download artifact(s): Artifact not found for name: pytorch_audio__3.10_xpu_x64

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• Build Windows Wheels / pytorch/audio / build-wheel-py3_10-xpu (gh) (trunk failure)
  Process completed with exit code 1.

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