Only allow async context manager in Py>=3.5

Author: nocarryr

pydispatch/utils.py

@@ -11,7 +11,7 @@
 if not PY2:
     basestring = str
 
-AIO_AVAILABLE = sys.version_info >= (3, 4)
+AIO_AVAILABLE = sys.version_info >= (3, 5)
 
 def get_method_vars(m):
     if PY2:

tests/conftest.py

@@ -1,7 +1,7 @@
 import sys
 import pytest
 
-AIO_AVAILABLE = sys.version_info >= (3, 4)
+AIO_AVAILABLE = sys.version_info >= (3, 5)
 
 collect_ignore = []
 if not AIO_AVAILABLE: