opentelemetry-instrumentation-boto3sqs: avoid KeyError when all messages in send_message_batch fail

[ferencjuhasz]

Description

Boto3SQSInstrumentor's send_message_batch wrapper unconditionally indexes retval["Successful"]:

retval = wrapped(*args, **kwargs)
for successful_messages in retval["Successful"]:

When every entry in a batch fails, the SQS SendMessageBatch response contains only Failed and omits the Successful key entirely. The wrapper then raises KeyError: 'Successful'. Because this happens inside the instrumentation wrapper, the exception propagates out of client.send_message_batch and breaks the caller — even though the failure is an ordinary per-message batch failure the application is expected to handle from the response.

File ".../boto3/resources/action.py", line 88, in __call__
File ".../opentelemetry/instrumentation/boto3sqs/__init__.py", line 270, in send_batch_wrapper
    for successful_messages in retval["Successful"]:
KeyError: 'Successful'

Fix

Iterate over retval.get("Successful", []). Spans for failed entries are still created and ended by the existing loop, so tracing behavior is otherwise unchanged.

Tests

The send_message_batch wrapper previously had no test coverage. This PR adds:

• test_send_message_batch — happy path: asserts the producer span per entry, full span attributes, and context propagation injection.
• test_send_message_batch_all_failed — regression test reproducing the KeyError when the response has no Successful key.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: ferencjuhasz / name: ferencjuhasz (302e81b, c6b4af7)

[xrmx]

@ferencjuhasz no need to rebase the changes, we'll take care of that at merge time, thanks!

[ferencjuhasz]

sorry about that, thanks!