Fix Python3 bug in THttpClient
Fix Python3 bug in THttpClient

Summary: 3 != >3

Differential Revision: D3352815

fbshipit-source-id: 996dcd7ee1f36e0e22afb9f51f05cbf35240ccde

LinusU/fbthrift,facebook/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,facebook/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,getyourguide/fbthrift,facebook/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,facebook/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,LinusU/fbthrift,LinusU/fbthrift,facebook/fbthrift,getyourguide/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift