Replace some type checks with six type checks

Signed-off-by: Adrian Tschira <nota@notafile.com>

contrib/graph/graph3.py

@@ -22,6 +22,8 @@ import argparse
 from synapse.events import FrozenEvent
 from synapse.util.frozenutils import unfreeze
 
+from six import string_types
+
 
 def make_graph(file_name, room_id, file_prefix, limit):
     print "Reading lines"
@@ -58,7 +60,7 @@ def make_graph(file_name, room_id, file_prefix, limit):
         for key, value in unfreeze(event.get_dict()["content"]).items():
             if value is None:
                 value = "<null>"
-            elif isinstance(value, basestring):
+            elif isinstance(value, string_types):
                 pass
             else:
                 value = json.dumps(value)