The code for _run() (called by run()) in server/host/ssh_host.py:

        result = utils.run(full_cmd, timeout, True, stdout, stderr,
                           verbose=False, stdin=stdin,
                           stderr_is_expected=ignore_status,
                           ignore_timeout=ignore_timeout)

This confuses me, and may be wrong.  From client/common_lib/base_utils.py:

    @param stderr_is_expected: if True, stderr will be logged at the same level
            as stdout

so that parameter only impacts logging.  If ignore_status is True (which cannot happen when called by ssh_host._run()), the call will return the status of the command, otherwise it will throw an exception when the status is non-zero.  Ssh_host.run() accepts the keyword parameter ignore_status, but doesn't document it.