Fix task SDK connection error handling to match airflow-core behavior

[amoghrajesh]

Unusual, but when Connection.get(None) is called, the stacktrace looks like:

[2025-09-30 16:58:30] WARNING - Skipping masking for a secret as it's too short (<5 chars) source=airflow._shared.secrets_masker.secrets_masker loc=secrets_masker.py:546
[2025-09-30 16:58:30] ERROR - Unable to retrieve connection from secrets backend (EnvironmentVariablesBackend). Checking subsequent secrets backend. source=task loc=context.py:162
AttributeError: 'NoneType' object has no attribute 'upper'
File "/opt/airflow/task-sdk/src/airflow/sdk/execution_time/context.py", line 156 in _get_connection

File "/opt/airflow/airflow-core/src/airflow/secrets/base_secrets.py", line 76 in get_connection

File "/opt/airflow/airflow-core/src/airflow/secrets/environment_variables.py", line 34 in get_conn_value

[2025-09-30 16:58:30] ERROR - Task failed with exception source=task loc=task_runner.py:993
ValidationError: 1 validation error for GetConnection
conn_id
  Input should be a valid string [type=string_type, input_value=None, input_type=NoneType]
    For further information visit https://errors.pydantic.dev/2.11/v/string_type
File "/opt/airflow/task-sdk/src/airflow/sdk/execution_time/task_runner.py", line 919 in run

File "/opt/airflow/task-sdk/src/airflow/sdk/execution_time/task_runner.py", line 1306 in _execute_task

File "/opt/airflow/task-sdk/src/airflow/sdk/bases/operator.py", line 416 in wrapper

File "/opt/airflow/providers/standard/src/airflow/providers/standard/operators/python.py", line 216 in execute

File "/opt/airflow/providers/standard/src/airflow/providers/standard/operators/python.py", line 239 in execute_callable

File "/opt/airflow/task-sdk/src/airflow/sdk/execution_time/callback_runner.py", line 82 in run

File "/files/dags/print_sensitive_data.py", line 13 in print_sensitive

File "/opt/airflow/task-sdk/src/airflow/sdk/definitions/connection.py", line 226 in get

File "/opt/airflow/task-sdk/src/airflow/sdk/execution_time/context.py", line 183 in _get_connection

File "/usr/python/lib/python3.10/site-packages/pydantic/main.py", line 253 in __init__

This is because when a connection is not found, the secrets backend failures log verbosely (log.exception) and continues to API call, allowing cryptic errors to bubble up. Changed that to log.debug, so that the task SDK now raises clean AirflowNotFoundException instead of cryptic AttributeError, matching airflow-core's error handling.

Example after:

from airflow.sdk import Connection as SDKConnection
SDKConnection.get(None)
Traceback (most recent call last):
  File "/Users/amoghdesai/Documents/OSS/repos/airflow/.venv/lib/python3.12/site-packages/IPython/core/interactiveshell.py", line 3699, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-9-21c62a62b135>", line 1, in <module>
    SDKConnection.get(None)
  File "/Users/amoghdesai/Documents/OSS/repos/airflow/task-sdk/src/airflow/sdk/definitions/connection.py", line 226, in get
    return _get_connection(conn_id)
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/amoghdesai/Documents/OSS/repos/airflow/task-sdk/src/airflow/sdk/execution_time/context.py", line 172, in _get_connection
    raise AirflowNotFoundException(f"The conn_id `{conn_id}` isn't defined")
airflow.exceptions.AirflowNotFoundException: The conn_id `None` isn't defined

---

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[github-actions]

Backport successfully created: v3-1-test

Status	Branch	Result
✅	v3-1-test