ubuntu-device-flash fails in CI context

[Ash Charles]

Hi,

I seeing an error when running this command:
sudo ubuntu-device-flash core 15.04 -o beagle.img --size 4 --oem
beagle.snap --enable-ssh --developer-mode

<error>
Determining oem configuration
2015/04/30 18:01:39 Signature check failed, but installing anyway as requested
mkdir /tmp/oem155078730/oem/beagle: permission denied
2015/04/30 18:01:39 Warning: failed to remove
/tmp/oem155078730/oem/beagle/0.1: %!s(<nil>)
2015-05-01 01:01:39 ERROR snappy logger.go:199 beagle.snap failed to
install: unpack beagle.snap to /tmp/oem155078730/oem/beagle/0.1 failed
with exit status 1
</error>
Full text (including command-line and environment variables) [1]

Look familiar to anyone?

The error only occurs when the command is run in the context of a
continuous integration system, buildbot, not when I run the command
manually.  Note: the buildbot has passwordless sudo for this command.

I apologize if this is the wrong forum for such a question---I'd love
a suggestion to a better place to pose the question if not.

--Ash
[1] https://buildbot.gumstix.com/builders/snappy-beagle-master/builds/10/steps/shell_2/logs/stdio