[Piglit] Redirect summary console output

[Jordan Justen]

Dylan,

I often send piglit summary console output to less or grep, but lately
it doesn't seem to work.

For example, if I try to send it to cat, I have to press Ctrl-C, and
then I see this output:

$ ./piglit summary console results/t | cat
^CTraceback (most recent call last):
  File "./piglit", line 107, in <module>
    import framework.programs.run as run
  File "/home/jljusten/src/fdo/piglit/framework/programs/run.py", line 32, in <module>
    from framework import core, backends, exceptions
  File "/home/jljusten/src/fdo/piglit/framework/backends/__init__.py", line 48, in <module>
    from .compression import COMPRESSION_SUFFIXES
  File "/home/jljusten/src/fdo/piglit/framework/backends/compression.py", line 98, in <module>
    subprocess.check_call(['xz'], stderr=d)
  File "/usr/lib/python2.7/subprocess.py", line 535, in check_call
    retcode = call(*popenargs, **kwargs)
  File "/usr/lib/python2.7/subprocess.py", line 522, in call
    return Popen(*popenargs, **kwargs).wait()
  File "/usr/lib/python2.7/subprocess.py", line 1384, in wait
    pid, sts = _eintr_retry_call(os.waitpid, self.pid, 0)
  File "/usr/lib/python2.7/subprocess.py", line 476, in _eintr_retry_call
    return func(*args)
KeyboardInterrupt

I guess it is related to xz support somehow...

-Jordan