Change some uses of cStringIO.StringIO to io.StringIO.
This is undoubtedly insufficient and in some cases just as broken as before.
diff --git a/Lib/SocketServer.py b/Lib/SocketServer.py
index 84bbcf6..8e92b80 100644
--- a/Lib/SocketServer.py
+++ b/Lib/SocketServer.py
@@ -577,10 +577,7 @@
     """Define self.rfile and self.wfile for datagram sockets."""
 
     def setup(self):
-        try:
-            from cStringIO import StringIO
-        except ImportError:
-            from StringIO import StringIO
+        from io import StringIO
         self.packet, self.socket = self.request
         self.rfile = StringIO(self.packet)
         self.wfile = StringIO()