NATS Client error while processing boolean header values

[ricardomfmartins]

I've detected that when we publish a message with headers that include boolean values (see example below), the NATS client fails with the error: 'bool' object has no attribute 'encode'

{"type": "GetStamp", "hasAvailableCapacity": True}

I saw that the _send_publish method inside the client.py is doing a value.encode(), which only supports header values of the type string.
Shouldn't accepting bool header values be a valid option?

[wallyqs]

Headers have to be strings, so have to stringify before sending. I was hoping that this would have resulted in a type error though...