We get the stack trace if a test failed:

Test output: ================================
09:11:34.584:     4: PASS

 <<< ================================
Traceback (most recent call last):
  File "zdtm.py", line 922, in <module>
    do_run_test(tinfo[0], tinfo[1], tinfo[2], tinfo[3])
  File "zdtm.py", line 696, in do_run_test
    t.kill()
  File "zdtm.py", line 302, in kill
    self.__flavor.fini()
  File "zdtm.py", line 168, in fini
    subprocess.check_call(["mount", "--make-private", self.root])
  File "/usr/lib64/python2.7/subprocess.py", line 540, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['mount', '--make-private', '/tmp/criu-root-YN1t3X']' returned non-zero exit status 32
umount: /tmp/criu-root-YN1t3X: not mounted

Cc: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Acked-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>