[Piglit] piglit summary output no longer greppable?

[Ilia Mirkin]

Hi Dylan,

Looks like something happened to piglit summary redirection... Note
that I had to hit ^C, or else nothing was coming out. Seems like the
xz check is somehow not getting its own separate stdout or something?

$ python piglit-summary.py asdf2 | grep fail
^CTraceback (most recent call last):
  File "piglit-summary.py", line 26, in <module>
    from framework.programs.summary import console
  File "/home/ilia/src/piglit/framework/programs/summary.py", line 30,
in <module>
    from framework import summary, status, core, backends, exceptions
  File "/home/ilia/src/piglit/framework/summary.py", line 41, in <module>
    from framework import grouptools, backends, exceptions
  File "/home/ilia/src/piglit/framework/backends/__init__.py", line
48, in <module>
    from .compression import COMPRESSION_SUFFIXES
  File "/home/ilia/src/piglit/framework/backends/compression.py", line
98, in <module>
    subprocess.check_call(['xz'], stderr=d)
  File "/usr/lib64/python2.7/subprocess.py", line 535, in check_call
    retcode = call(*popenargs, **kwargs)
  File "/usr/lib64/python2.7/subprocess.py", line 522, in call
    return Popen(*popenargs, **kwargs).wait()
  File "/usr/lib64/python2.7/subprocess.py", line 1384, in wait
    pid, sts = _eintr_retry_call(os.waitpid, self.pid, 0)
  File "/usr/lib64/python2.7/subprocess.py", line 476, in _eintr_retry_call
    return func(*args)
KeyboardInterrupt