Exception AttributeError: "'Popen' object has no attribute '_child_created'"

* This error is when cleaning up, so the image is already successfully generated when you see it. *

Got this when creating a panda image.
This was on revno: 282

sudo ~/work/linaro/linaro-image-tools/linaro-media-create --rootfs ext3 --mmc /dev/mmcblk0 --dev panda --swap_file 256 --hwpack hwpack_linaro-panda_20110201-0_armel_supported.tar.gz --binary linaro-natty-efl-tar-20110201-1.tar.gz --hwpack-force-yes

...
256+0 records in
256+0 records out
268435456 bytes (268 MB) copied, 35.9356 s, 7.5 MB/s
mkswap: /tmp/tmpyhTbtO/root-disc/SWAP.swap: warning: don't erase bootbits sectors
        on whole disk. Use -f to force.
Setting up swapspace version 1, size = 262140 KiB
no label, UUID=cb1e11b2-cb8f-497d-b679-e70aab4d9c91

Creating /etc/flash-kernel.conf

Done creating Linaro image on /dev/mmcblk0
Exception AttributeError: "'Popen' object has no attribute '_child_created'" in <bound method Popen.__del__ of <linaro_media_create.cmd_runner.Popen object at 0x17a8950>> ignored
Error in atexit._run_exitfuncs:
Traceback (most recent call last):
  File "/usr/lib/python2.7/atexit.py", line 24, in _run_exitfuncs
    func(*targs, **kargs)
  File "/home/plars/work/linaro/linaro-image-tools/linaro-media-create", line 73, in cleanup_tempdir
    except SubcommandNonZeroReturnValue:
NameError: global name 'SubcommandNonZeroReturnValue' is not defined
Error in sys.exitfunc:
Traceback (most recent call last):
  File "/usr/lib/python2.7/atexit.py", line 24, in _run_exitfuncs
    func(*targs, **kargs)
  File "/home/plars/work/linaro/linaro-image-tools/linaro-media-create", line 73, in cleanup_tempdir
    except SubcommandNonZeroReturnValue:
NameError: global name 'SubcommandNonZeroReturnValue' is not defined