TypeError at S3 file retrieval

[I159]

During boto3.resource('s3').Object(bucket, key).get() TypeError raised and invalid json is recorded, while a response is totally valid. bytes type is not json serializable. And response body is a file which is of bytes type. But this is not a reason to raise an error and record invalid json. I propose to stub body with empty value and finish recording without error because lack of file is not an issue for unit testing but invalid record is.

[I159]

A PR to discuss #70