fix(infra): correct mock.patch target for build_image_impl in helper_test

[Ravi-Dahiya-00]

What changed

In ShellTest.test_base_runner_debug inside infra/helper_test.py, the mock decorator was incorrectly targeting helper.build_image_impl:

# Before (incorrect)
@mock.patch('helper.build_image_impl')

# After (correct)
@mock.patch('common_utils.build_image_impl')

Why it was wrong

build_image_impl is defined in common_utils.py, not in helper.py.

Python's unittest.mock.patch works by replacing the name at the location where it is defined (or where it is imported and used). Since helper.build_image_impl does not exist as a name in the helper module, the patch had no effect — the real build_image_impl function was being called silently during the test, making it neither a true unit test nor reliable in environments without Docker.

Impact

• The test test_base_runner_debug was not actually isolating the unit under test.
• Any side effects from the real build_image_impl (e.g., Docker calls) could cause non-deterministic failures in CI.
• This fix ensures the mock is applied correctly so the test runs fast, isolated, and without external dependencies.

No functional changes

Only the test file is modified. No production code is affected.

[Ravi-Dahiya-00]

@mikeal @alex @bgianfo @haberman hii could you please check it out.

[alex]

Do not ping random users. It's incredible rude. (I'm not a maintainer of this project at all.)

[Ravi-Dahiya-00]

Do not ping random users. It's incredible rude. (I'm not a maintainer of this project at all.)

Sorry, dude. It was just a mistake. I thought you were a maintainer because you have such an awesome profile, man. 😅