Producer. Connection or connection error handling

Description
===========

Code runs before connection has been established.

How to reproduce
================
```
....
producer = Producer(config);
print('CONNECTED')
....
```

Checklist
=========
Please provide the following information:
- [X] Critical issue

the code above prints CONNECTED before connection of even connection timeout or error.

how to handle connection result? is there some some parameters where i could set a callback?

documentation https://docs.confluent.io/platform/current/clients/confluent-kafka-python/html/index.html#producer does not discover the config parameters properly