Use BytesIO and StringIO from io instead of six

slapos/networkbench/__init__.py

@@ -13,7 +13,7 @@ import random
 import pycurl
 import argparse
 import json
-from six import StringIO
+from io import StringIO
 from .ping import ping, ping6
 from .dnsbench import resolve
 from .http import get_curl, request

slapos/networkbench/http.py

 import sys
 import pycurl
-from six import BytesIO
+from io import BytesIO
 
 def get_curl(buffer, url):
   curl = pycurl.Curl()