Make the version check more strict

src/python/grpcio_health_checking/grpc_health/v1/health.py

@@ -21,7 +21,7 @@ import grpc
 from grpc_health.v1 import health_pb2 as _health_pb2
 from grpc_health.v1 import health_pb2_grpc as _health_pb2_grpc
 
-if sys.version_info[0] > 2:
+if sys.version_info[0] >= 3 and sys.version_info[1] >= 6:
     from ._async import AsyncHealthServicer
 
 SERVICE_NAME = _health_pb2.DESCRIPTOR.services_by_name['Health'].full_name