test: Fix failing SDK test by replacing mock.patch with subprocess for actual build

[DharmitD]

Description of your changes: Resolves: https://github.com/kubeflow/pipelines/issues/11038

• Removed the mock.patch on subprocess.run.
• Added a direct call to subprocess.run to build the KFP package.
• Introduced error handling with a helpful error message if the package build fails.
• Kept the rest of the test logic intact.

The original mock.patch.object wasn’t working because it prevented the real build from happening, which was necessary for the test to pass. Replacing it with a direct call to subprocess.run ensures the KFP package is actually built, resolving the issue. This approach allows the test to reflect the real build environment and provides clearer error reporting if something goes wrong during the build process.

SDK test GHA passed on this PR: https://github.com/kubeflow/pipelines/actions/runs/11284347350/job/31385382544?pr=11285 Alternatively, you could test locally by running the following command from the repo's root directory:

pytest sdk/python/kfp --ignore=sdk/python/kfp/deprecated --cov=kfp

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[DharmitD]

ready for review. cc: @chensun @gregsheremeta @connor-mccarthy @hbelmiro

[gregsheremeta]

what was the mock.patch.object supposed to be doing, why wasn't it working, and how does calling a build via subprocess act as a valid replacement? (The commit message and PR should explain this, too.)

[google-oss-prow[bot]]

New changes are detected. LGTM label has been removed.

[DharmitD]

what was the mock.patch.object supposed to be doing, why wasn't it working, and how does calling a build via subprocess act as a valid replacement? (The commit message and PR should explain this, too.)

Done, added some details on this in the commit message and the PR description.

[VaniHaripriya]

/rerun-all