Comment 4 for bug 1164028

I'm seeing the same failure here with the console being hijacked is is causing an issue with checkbox.

With that said,

1.) The shell=True argument is in fact necessary, otherwise the generated VM boot messages are never forwarded to the virt.debug log.
2.) Problem number 1 results in the fact that the test will never be successful due to the VM console output never being available anywhere due to the omission of shell=True.
3.) Killing the VM unfortunately doesn't fix any of this.

So, with that said we have a few options

1.) Figure out where we can redirect the console output of the VM without disrupting or hijacking the console terminal in which the python script runs.
2.) Configure the cloud data supplied to VM to create an ssh key and IP address so that we can connect to it later, or some other cloud-init verification means.