[Piglit] failed assertion in json_.py

[Brian Paul]

I'm not sure when this started (haven't bisected it yet).  But when I 
run a test like this I'm getting an assertion:

$ ./piglit-run.py -v -t ext_transform_feedback tests/all.tests results/xfb

[0/0]  Running Test(s): 0
Traceback (most recent call last):
   File "./piglit-run.py", line 32, in <module>
     run(sys.argv[1:])
   File "/home/brian/projects/piglit/framework/programs/run.py", line 
287, in run
     backend.finalize({'time_elapsed': results.time_elapsed})
   File "/home/brian/projects/piglit/framework/backends/json_.py", line 
127, in finalize
     assert data['tests']
AssertionError


Any ideas?

-Brian