chore: release main - #18293

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@PACKAGE (FAILED): google-cloud-spanner
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Activated service account credentials for: [kokoro@precise-truck-742.iam.gserviceaccount.com]
/tmpfs/src/github/google-cloud-python/packages/google-cloud-spanner
nox > Running session system-3.12(protobuf_implementation='python', database_dialect='GOOGLE_STANDARD_SQL')
nox > uv binary not found.
nox > Creating virtual environment (virtualenv) using python3 in .nox/system-3-12-protobuf_implementation-python-database_dialect-google_standard_sql
nox > python -m pip install --pre 'grpcio!=1.52.0rc1'
nox > python -m pip install mock pytest pytest-asyncio google-cloud-testutils -c /tmpfs/src/github/google-cloud-python/packages/google-cloud-spanner/testing/constraints-3.12.txt
nox > python -m pip install -e '.[tracing]' -c /tmpfs/src/github/google-cloud-python/packages/google-cloud-spanner/testing/constraints-3.12.txt
nox > py.test --quiet -o asyncio_mode=auto --junitxml=system_3.12_sync_sponge_log.xml tests/system --ignore=tests/system/_async
sssssssss....................................s.......................... [ 33%]
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=================================== FAILURES ===================================
______________________________ test_table_exists _______________________________

shared_database = 

    def test_table_exists(shared_database):
        table = shared_database.table("all_types")
>       assert table.exists()
               ^^^^^^^^^^^^^^

tests/system/test_table_api.py:24: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
google/cloud/spanner_v1/table.py:101: in exists
    with self._database.snapshot() as snapshot:
         ^^^^^^^^^^^^^^^^^^^^^^^^^
google/cloud/spanner_v1/database.py:1477: in __exit__
    self._session.create()
google/cloud/spanner_v1/session.py:201: in create
    session_pb = api.create_session(
google/cloud/spanner_v1/services/spanner/client.py:749: in create_session
    response = rpc(
.nox/system-3-12-protobuf_implementation-python-database_dialect-google_standard_sql/lib/python3.12/site-packages/google/api_core/gapic_v1/method.py:189: in __call__
    return wrapped_func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.nox/system-3-12-protobuf_implementation-python-database_dialect-google_standard_sql/lib/python3.12/site-packages/google/api_core/retry/retry_unary.py:295: in retry_wrapped_func
    return retry_target(
.nox/system-3-12-protobuf_implementation-python-database_dialect-google_standard_sql/lib/python3.12/site-packages/google/api_core/retry/retry_unary.py:157: in retry_target
    next_sleep = _retry_error_helper(
.nox/system-3-12-protobuf_implementation-python-database_dialect-google_standard_sql/lib/python3.12/site-packages/google/api_core/retry/retry_base.py:215: in _retry_error_helper
    raise final_exc from source_exc
.nox/system-3-12-protobuf_implementation-python-database_dialect-google_standard_sql/lib/python3.12/site-packages/google/api_core/retry/retry_unary.py:148: in retry_target
    result = target()
             ^^^^^^^^
.nox/system-3-12-protobuf_implementation-python-database_dialect-google_standard_sql/lib/python3.12/site-packages/google/api_core/timeout.py:130: in func_with_timeout
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^