DynamoDB: transact_write_items does not return Item in CancellationReasons

[EmmaStott]

moto 5.0.3 does not return Item under err.response["CancellationReasons"][n] when a transaction fails, despite setting "ReturnValuesOnConditionCheckFailure": "ALL_OLD"

This appears to be a regression of #5204

Comparing 970aee3 to the latest version https://github.com/getmoto/moto/blob/master/moto/dynamodb/exceptions.py#L232-L256, it looks like the fix was dropped somewhere along the line.

[bblommers]

Hi @EmmaStott! We have a unit test for this, which asserts that we do return the item:

moto/tests/test_dynamodb/test_dynamodb.py

Line 3805 in 1fc2200

def test_transact_write_items_failure__return_item(table_name=None):

Can you share a reproducible test case where it is not being returned?

[bblommers]

Going to close this due to a lack of response - if there is a reproducible case I'd be happy to reopen.