When the config_enable bot creates the Config bucket it uses the S3 ServiceResource's create_bucket() method:
result = s3_resource.create_bucket(...)
It then refers to that result as if it were a call the the S3 Client's create_bucket() method:
responseCode = result['ResponseMetadata']['HTTPStatusCode']
This is invalid, as the S3 Resource returns an instance of s3.Bucket, not a dict, so it throws a ClientError: TypeError: 's3.Bucket ' object is not subscriptable.
In fact it does not need to check the result since we already know that the create_bucket() must have succeeded if the execution reaches that line.