James, actual error -- steps to reproduce:
* start new clean natty schroot
* install linaro-image-tools build-deps
* enter chroot from clean env
env -i schroot -c natty-f1175172-fda1-42cc-a6d6-91b7346482d5 -r /bin/bash
* run testsuite


 python -m testtools.run tests.test_suite           
Tests running...
tar: Removing leading `/' from member names
tar: /tmp/tmpFISN5j: file changed as we read it
======================================================================
ERROR: linaro_media_create.tests.test_media_create.TestCreatePartitions.test_run_sfdisk_commands
----------------------------------------------------------------------
Text attachment: traceback
------------
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/testtools/runtest.py", line 169, in _run_user
    return fn(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/testtools/testcase.py", line 499, in _run_test_method
    return self._get_test_method()()
  File "linaro_media_create/tests/test_media_create.py", line 598, in test_run_sfdisk_commands
    stderr=subprocess.PIPE)
  File "linaro_media_create/partitions.py", line 287, in run_sfdisk_commands
    as_root=as_root)
  File "linaro_media_create/cmd_runner.py", line 45, in run

    return Popen(args, stdin=stdin, stdout=stdout, stderr=stderr)
  File "linaro_media_create/cmd_runner.py", line 60, in __init__
    super(Popen, self).__init__(args, env=env, **kwargs)
  File "/usr/lib/python2.7/subprocess.py", line 672, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1206, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory
------------
======================================================================
ERROR: linaro_media_create.tests.test_media_create.TestCreatePartitions.test_run_sfdisk_commands_raises_on_non_zero_returncode
----------------------------------------------------------------------
Text attachment: traceback
------------
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/testtools/runtest.py", line 169, in _run_user
    return fn(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/testtools/testcase.py", line 499, in _run_test_method
    return self._get_test_method()()
  File "linaro_media_create/tests/test_media_create.py", line 607, in test_run_sfdisk_commands_raises_on_non_zero_returncode

    stderr=subprocess.PIPE)
  File "/usr/lib/python2.7/dist-packages/testtools/testcase.py", line 318, in assertRaises
    ret = callableObj(*args, **kwargs)
  File "linaro_media_create/partitions.py", line 287, in run_sfdisk_commands
    as_root=as_root)
  File "linaro_media_create/cmd_runner.py", line 45, in run
    return Popen(args, stdin=stdin, stdout=stdout, stderr=stderr)
  File "linaro_media_create/cmd_runner.py", line 60, in __init__
    super(Popen, self).__init__(args, env=env, **kwargs)
  File "/usr/lib/python2.7/subprocess.py", line 672, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1206, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory
------------
======================================================================
ERROR: linaro_media_create.tests.test_media_create.TestPartitionSetup.test_calculate_partition_size_and_offset
----------------------------------------------------------------------
Text attachment: traceback
------------
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/testtools/runtest.py", line 169, in _run_user

    return fn(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/testtools/testcase.py", line 499, in _run_test_method
    return self._get_test_method()()
  File "linaro_media_create/tests/test_media_create.py", line 637, in test_calculate_partition_size_and_offset
    tempfile = self._create_qemu_img_with_partitions(',1,0x0C,*\n,,,-')
  File "linaro_media_create/tests/test_media_create.py", line 678, in _create_qemu_img_with_partitions
    stderr=subprocess.PIPE)
  File "linaro_media_create/partitions.py", line 287, in run_sfdisk_commands
    as_root=as_root)
  File "linaro_media_create/cmd_runner.py", line 45, in run
    return Popen(args, stdin=stdin, stdout=stdout, stderr=stderr)
  File "linaro_media_create/cmd_runner.py", line 60, in __init__
    super(Popen, self).__init__(args, env=env, **kwargs)
  File "/usr/lib/python2.7/subprocess.py", line 672, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1206, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory
------------

======================================================================
ERROR: linaro_media_create.tests.test_media_create.TestPartitionSetup.test_get_boot_and_root_loopback_devices
----------------------------------------------------------------------
Text attachment: traceback
------------
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/testtools/runtest.py", line 169, in _run_user
    return fn(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/testtools/testcase.py", line 499, in _run_test_method
    return self._get_test_method()()
  File "linaro_media_create/tests/test_media_create.py", line 698, in test_get_boot_and_root_loopback_devices
    tempfile = self._create_qemu_img_with_partitions(',1,0x0C,*\n,,,-')
  File "linaro_media_create/tests/test_media_create.py", line 678, in _create_qemu_img_with_partitions
    stderr=subprocess.PIPE)
  File "linaro_media_create/partitions.py", line 287, in run_sfdisk_commands
    as_root=as_root)
  File "linaro_media_create/cmd_runner.py", line 45, in run
    return Popen(args, stdin=stdin, stdout=stdout, stderr=stderr)
  File "linaro_media_create/cmd_runner.py", line 60, in __init__
    super(Popen, self).__init__(args, env=env, **kwargs)

  File "/usr/lib/python2.7/subprocess.py", line 672, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1206, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory
------------
======================================================================
ERROR: linaro_media_create.tests.test_media_create.TestPartitionSetup.test_setup_partitions_for_block_device
----------------------------------------------------------------------
Text attachment: traceback
------------
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/testtools/runtest.py", line 169, in _run_user
    return fn(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/testtools/testcase.py", line 499, in _run_test_method
    return self._get_test_method()()
  File "linaro_media_create/tests/test_media_create.py", line 767, in test_setup_partitions_for_block_device
    tempfile = self._create_qemu_img_with_partitions(',1,0x0C,*\n,,,-')
  File "linaro_media_create/tests/test_media_create.py", line 678, in _create_qemu_img_with_partitions
    stderr=subprocess.PIPE)
  File "linaro_media_create/partitions.py", line 287, in run_sfdisk_commands
    as_root=as_root)
  File "linaro_media_create/cmd_runner.py", line 45, in run
    return Popen(args, stdin=stdin, stdout=stdout, stderr=stderr)
  File "linaro_media_create/cmd_runner.py", line 60, in __init__
    super(Popen, self).__init__(args, env=env, **kwargs)
  File "/usr/lib/python2.7/subprocess.py", line 672, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1206, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory
------------
======================================================================
ERROR: linaro_media_create.tests.test_media_create.TestPartitionSetup.test_setup_partitions_for_image_file
----------------------------------------------------------------------
Text attachment: traceback
------------
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/testtools/runtest.py", line 169, in _run_user
    return fn(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/testtools/testcase.py", line 499, in _run_test_method
    return self._get_test_method()()
  File "linaro_media_create/tests/test_media_create.py", line 730, in test_setup_partitions_for_image_file
    tempfile = self._create_qemu_img_with_partitions(',1,0x0C,*\n,,,-')
  File "linaro_media_create/tests/test_media_create.py", line 678, in _create_qemu_img_with_partitions
    stderr=subprocess.PIPE)
  File "linaro_media_create/partitions.py", line 287, in run_sfdisk_commands
    as_root=as_root)
  File "linaro_media_create/cmd_runner.py", line 45, in run
    return Popen(args, stdin=stdin, stdout=stdout, stderr=stderr)
  File "linaro_media_create/cmd_runner.py", line 60, in __init__
    super(Popen, self).__init__(args, env=env, **kwargs)
  File "/usr/lib/python2.7/subprocess.py", line 672, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1206, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory
------------
Ran 388 tests in 9.256s

FAILED (failures=6)