On Python 3.x, hex returns a unicode string:
```
Python 3.2.3 (default, Oct 19 2012, 19:53:16) 
>>> import uuid
>>> uuid.uuid4().hex
'18e24a180d0e4e0ea24d61720e51fe80'
>>> uuid.uuid4().hex.encode()
b'151dfacb4d8f4e5e92ce5305473fff81'
```
The value is being used in kazoo.client.create which requires a binary string. Without encode, build fails on Python 3.x, see https://travis-ci.org/python-zk/kazoo/builds/5419920