Don't produce empty stderr/stdout files

This bug was fixed in the package autopkgtest - 2.9

---------------
autopkgtest (2.9) unstable; urgency=low

  New features:
  * Add "downtmp-host=<path>" testbed capability, for runners which can set up
    a shared directory between host and testbed. This is used by copyupdown to
    more efficiently copy files back and forth, and in many/most cases, don't
    explicitly copy anything at all.
  * Introduce a new testbed capability "downtmp-shared-fifo" that declares
    that testbed and the host can use a FIFO in the shared downtmp for
    communication. Use this to generalize live test output to all runners
    which declare that, not just -null.
  * Convert null, chroot, schroot, lxc, and qemu runners to use a shared
    downtmp dir. Note that qemu does not support FIFO (through the 9p file
    system), so that one does not get live test output.
  * Don't define $TMPDIR for tests any more. Having $TMPDIR in the shared dir
    isn't efficient and even breaks some tests (as they might not be able to
    put sockets etc. into it), and it's an artificial difference to the
    default system behaviour of just using /tmp. The documentation already was
    changed a long time ago to only document $ADTTMP as a scratch directory
    for tests.
  * Add test restrictions "isolation-container" and "isolation-machine", and
    corresponding testbed capabilities. Tests can use that to declare that
    they want to start services or open ports (i. e. a simple chroot/schroot
    is insufficient) or access hardware, reboot, and interact the kernel
    (where even a container is insufficient), and will be skipped instead of
    failing when they run in a virtualization server which does not provide
    enough isolation.
  * Add manpage for adt-build-lxc script.
  * Ship adt-build-lxc script and its manpage in the package.

  Documentation updates:
  * doc/README.package-tests: Some stylistic updates, and add section headers.
  * adt-virt-lxc.1: Point to, and show how to use adt-build-lxc.
  * Add doc/README.running-tests: Overview of how to run adt-run, most common
    scenarios, and available virtualization servers with their pros/cons.

  Bug fixes:
  * tests: Copy tests/home/ into a temporary dir and set $HOME to that, to
    avoid cluttering the source dir.
  * Don't produce empty stderr/stdout files with --output-dir. (LP: #1282866)
  * adt-buildvm-ubuntu-cloud: Install linux-generic, to get the full kernel
    (needed for e. g. udisks2 to get scsi_debug).
  * tests: Add a broken symlink to testpkg, to ensure that copying trees
    around gets along with those.
  * adt-run: Always use fakeroot with adt-virt-qemu, to work around chown
    failing on 9p.
  * xen/initscript: Always source /lib/lsb/init-functions. (Thanks lintian)
  * tests/adt-run: Increase timeout in NullRunner.test_timeout_long_build to
    avoid failure on slow architectures.
  * adt-build-lxc: Properly wait for finished container boot instead of a
    static 10 second sleep.
  * adt-build-lxc: Only flush the cache when updating an existing container.

 -- Martin Pitt <email address hidden> Thu, 27 Feb 2014 11:23:32 +0100