#2503 make singletons compared with "is" not == or !=
Thanks to Wummel for the patch
diff --git a/Demo/rpc/nfsclient.py b/Demo/rpc/nfsclient.py
index c4387b4..09e78dd 100644
--- a/Demo/rpc/nfsclient.py
+++ b/Demo/rpc/nfsclient.py
@@ -129,7 +129,7 @@
         self.unpacker = NFSUnpacker('')
 
     def mkcred(self):
-        if self.cred == None:
+        if self.cred is None:
             self.cred = rpc.AUTH_UNIX, rpc.make_auth_unix_default()
         return self.cred
 
@@ -170,7 +170,7 @@
             for fileid, name, cookie in entries:
                 list.append((fileid, name))
                 last_cookie = cookie
-            if eof or last_cookie == None:
+            if eof or last_cookie is None:
                 break
             ra = (ra[0], last_cookie, ra[2])
         return list
@@ -184,7 +184,7 @@
     else: filesys = None
     from mountclient import UDPMountClient, TCPMountClient
     mcl = TCPMountClient(host)
-    if filesys == None:
+    if filesys is None:
         list = mcl.Export()
         for item in list:
             print item