Thank you! There is a memory leak somewhere:

$ ./python -m test -R 3:2 test_generators
[1/1] test_generators
beginning 5 repetitions
12345
.....
test_generators leaked [1945, 1945] references, sum=3890
1 test failed:
    test_generators


Also, since the patch is so short, a stylistic nit:

+            if(tb == NULL) {

There should be a space after the "if".
(see PEP 7: http://www.python.org/dev/peps/pep-0007/)