Output from stderr/stdout should be retrieved from the buildslave. According to the answer I got on #buildbot it seems that some hacking on buildbot's ShellCommand is needed since buildbot doesn't keep separate stdout/stderr.
@mkrizek Is this ticket still valid? We seem to capture stream output from buildslaves just fine.
With disposable clients this is no longer valid. Closing.
Metadata Update from @mkrizek: - Issue tagged with: infrastructure