access_key is required even if machine has an IAM role attached

[shacharbz]

running on a remote aws windows host with an IAM role to enable s3 access.
I manage to download the file using:
win_shell: Read-S3Object -BucketName "{{ bucket_name }}" -Key "{{ key_name }}" -File "{{ temp_dir }}\some-file.txt"

but when trying to use win_s3 I get:
An exception occurred during task execution. To see the full traceback, use -vvv. The error was: + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fatal: [173.15.26.17]: FAILED! => {"changed": false, "failed": true, "msg": "The property 'access_key' cannot be found on this object. Verify that the property exists."}