Merge pull request kragniz#978 from ahmedbilal/patch-2

Don't close grpcio channel when it don't exist

Author: kragniz

etcd3/client.py

@@ -170,7 +170,8 @@ def __init__(self, host='localhost', port=2379,
 
     def close(self):
         """Call the GRPC channel close semantics."""
-        self.channel.close()
+        if hasattr(self, 'channel'):
+            self.channel.close()
 
     def __enter__(self):
         return self