Py3k fixes

Demos/callback/run_cheese.py

 import cheese
 
 def report_cheese(name):
-    print "Found cheese:", name
+    print("Found cheese: " + name)
 
 cheese.find(report_cheese)
 

Demos/pyprimes.py

@@ -4,7 +4,7 @@ def primes(kmax):
     n = 2
     while k < kmax:
         i = 0
-        while i < k and n % p[i] <> 0:
+        while i < k and n % p[i] != 0:
             i = i + 1
         if i == k:
             p.append(n)