Mark two logger tests as flaky

[amyeroberts]

What does this PR do?

Two tests which capture and check the logger's output occasionally fail.

FAILED tests/test_modeling_utils.py::ModelUtilsTest::test_model_from_pretrained_with_different_pretrained_model_name - AssertionError: False is not true
FAILED tests/test_modeling_utils.py::ModelUtilsTest::test_unexpected_keys_warnings - AssertionError: "were not used when initializing ModelWithHead: ['added_key']" not found in ''

It looks like the logger isn't capturing the output. I have never been able to replicate the errors outside of circle CI, locally or on a VM.

The reason for the failure is unclear: there are other tests in the same module which utilise CaptureLogger. However, it's always these two tests which fail.

Example runs, where failing tests were unrelated to the PR:

• https://app.circleci.com/pipelines/github/huggingface/transformers/81004/workflows/4919e5c9-0ea2-457b-ad4f-65371f79e277/jobs/1038999
• https://app.circleci.com/pipelines/github/huggingface/transformers/82051/workflows/8674dab8-35ac-4336-8db2-24d90426554f/jobs/1054942

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[ydshieh]

Thanks. I could take a look in the future. Would be nice to provide the error message or a link of the run page using description= in is_flaky

[amyeroberts]

@ydshieh Sure, will add!

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