Normally, the dispatcher is supposed to wait for the command prompt before issuing a new command to the target. This way we ensure that the previous command has finished before trying to execute the next one. For some reason, however, I occasionally see a situation where it sends a line before the previous one has finished. For example:
http://validation.linaro.org/jenkins/job/Lava%20Daily%20Beaglexm01/imagetype=alip,target=beaglexm01%20omap3/17/
From this, you can see, that during the install of packages prior to installing lava-test, the bzr branch lp:lava-test command is sent. This doesn't end up running though, and the test fails because it sees that lava-test is not installed.
What I suspect is happening, is perhaps we are getting more than one match for the shell prompt at some point. expect can catch something in the buffer, even if it didn't get sent after the previous command. It may be worth considering trashing the buffer before sending a new command, but I'm not sure if this will be sufficient.
I'd like to try to get this one fixed soon, I have a sneaking suspicion that it can sometimes lead to things failing when they shouldn't.