What does this PR do?

Print error logs from launcher during integration tests

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• [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• [ ] Did you write any new necessary tests?

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@OlivierDehaene OR @Narsil

Hey @Atry thanks for the contribution.

Do you mind sharing a bit more about the problem this is trying to solve ?

I should be able to see error logs from the launcher's stderr, when running integration tests. The error logs are useful to debug failed tests.

But that's already the case with the -s pytest arg isn't it?

The -s option affects how to capture pytest's stdout and stderr, but it does not affect launcher's stderr in the current implementation, because launcher's stderr is not forwarded to pytest.

This PR redirects launcher's stderr to launcher's stdout, which is already forwarded to pytest's stderr at https://github.com/huggingface/text-generation-inference/pull/480/files#diff-f99db5aabf9de5120c24409d7be1b79e635a807f5dc3c12de0116b66f5528be2R256, solving this problem.

Hi @OlivierDehaene, could you trigger the CI for this PR? You will see more logs than the main branch.