When terminating a session on a downed agent, tladm behaves as if things are just fine. Since the agent is down, it's impossible to kill the session. This should be indicated to the user.
See also bug 1559, which seems like about the same piece of code.
New code. Check if problem remains.
Problem remains, but this is due to the VSM server reporting no error. A remote kill_session call to VSM server results in server data {'errcode': 0, 'result': 0}.
This is a bit different these days. We now have better handling of downed agents, and the interface will change a bit if the agent is unresponsive. It now prints a warning that the session cannot be verified, and the button changes text to "Abandon". However you still get no warning if the agent becomes unresponsive after opening the session details, and I'm not sure if other failures are handled either.