Fix flaky GCS bucket deletion in test_create_default_bucket

[aIbrahiim]

Fixes: #30513

Error from logs: google.api_core.exceptions.NotFound: 404 DELETE https://storage.googleapis.com/storage/v1/b/gcsio-it-735-us-central1-d3d66207-1762710421?prettyPrint=false: The specified bucket does not exist.

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[gemini-code-assist]

Summary of Changes

Hello @aIbrahiim, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a recurring flakiness issue in the GCS integration tests, specifically within the test_create_default_bucket method. The previous implementation could fail with a NotFound error if it attempted to delete a GCS bucket that no longer existed. The changes introduce a check to verify the bucket's presence before deletion and gracefully handle NotFound exceptions, making the test more reliable and stable.

Highlights

• Flaky Test Fix: Addressed a flaky GCS bucket deletion in test_create_default_bucket by ensuring the bucket exists before attempting to delete it.
• Error Handling: Implemented robust error handling for bucket deletion by catching NotFound exceptions, preventing test failures if the bucket is already gone.

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[aIbrahiim]

@damccorm May you review please.

[damccorm]

This change is changing the underlying test - if the bucket doesn't exist, that means that we should be failing the test (this just covers up potentially flaky actual behavior). Do you know why this is happening? Is it because tests are overwriting the same bucket name, a timing issue, or are we actually failing to create these buckets?

[aIbrahiim]

Ahh absolutely right, then this masks the issue as I wasn't aware that the test should fail if bucket doesnt exists but when i was investigating the test class i found out that:
get_or_create_default_gcs_bucket() creates/gets bucket by create_bucket()
then wait 60 seconds for propagation
then it asserts the bucket exists using the object returned from creation
after that it make a fresh call by get_bucket() to lookup_bucket() which may hit a different gcs endpoint or cache layer
even after the 60 seconds wait lookup_bucket() might not immediately see the newly created bucket maybe because
different api endpoints create_bucket or lookup_bucket having different cache states or gcs eventual consistency across regions or even caches, also does create_bucket() and lookup_bucket() may hit different gcs endpoints or caches?
and it might be name collisions as multiple test runs using the same random bucket names?

[damccorm]

Before doing this, could we try retrying the call on failure several times (maybe 5)? Then if the bucket still is not found, we can pass

Also, how often is this flaking?

[aIbrahiim]

Based on the last 9 runs, we have 2 failures out of 8 completed runs (excluding 1 cancelled), giving us a 25%

[github-actions]

Checks are failing. Will not request review until checks are succeeding. If you'd like to override that behavior, comment assign set of reviewers

[damccorm]

Thanks