Fix support for python 3.4 <= 3.4.2

asyncio module is provisional, which means it gets updated everytime

slixmpp/__init__.py

@@ -7,7 +7,8 @@
 """
 
 import asyncio
-asyncio.sslproto._is_sslproto_available=lambda: False
+if hasattr(asyncio, 'sslproto'): # no ssl proto: very old asyncio = no need for this
+    asyncio.sslproto._is_sslproto_available=lambda: False
 import logging
 logging.getLogger(__name__).addHandler(logging.NullHandler())