I got this in the logs, running integration tests with the latest version of Elasticsearch.

```
09:36:03,768 (elasticsearch[ip-172-30-1-45.ec2.internal][http_server_worker]T#4) WARN RestExplainAction:247 - [types removal] Specifying a type in explain requests is deprecated.
```

Not sure to which versions it applies exactly, we'll have to check.