Example builds:

https://luci-milo.appspot.com/buildbot/chromeos/link-paladin/28275
https://luci-milo.appspot.com/buildbot/chromeos/link-paladin/28269

05/10 13:49:52.905 DEBUG|              test:0379| starting test(run_once()), test details follow
()
05/10 13:49:52.914 DEBUG|        cryptohome:0476| Issued call <dbus.proxies._DeferredMethod instance at 0x7fdb826238c0> with async_id 19
05/10 13:49:52.915 DEBUG|        cros_disks:0133| Waiting for D-Bus signal "AsyncCallStatus"
05/10 13:49:52.916 DEBUG|        cros_disks:0138| Received D-Bus signal "AsyncCallStatus({'return_status': dbus.Boolean(True), 'async_id': dbus.Int32(19), 'return_code': dbus.Int32(0)})"
05/10 13:49:52.918 DEBUG|        cryptohome:0476| Issued call <dbus.proxies._ProxyMethod instance at 0x7fdb82601d40> with async_id 20
05/10 13:49:52.919 DEBUG|        cros_disks:0133| Waiting for D-Bus signal "AsyncCallStatus"
05/10 13:49:53.321 DEBUG|        cros_disks:0138| Received D-Bus signal "AsyncCallStatus({'return_status': dbus.Boolean(False), 'async_id': dbus.Int32(20), 'return_code': dbus.Int32(2)})"
05/10 13:49:53.325 DEBUG|              test:0389| Test failed due to org.chromium.SessionManagerInterface.NoUserNssDb: Can't create session.. Exception log follows the after_iteration_hooks.
05/10 13:49:53.326 DEBUG|              test:0392| starting after_iteration_hooks
05/10 13:49:53.327 DEBUG|             utils:0202| Running 'mkdir -p /usr/local/autotest/results/default/login_MultipleSessions/sysinfo/iteration.1/var/spool'
05/10 13:49:53.338 DEBUG|             utils:0202| Running 'rsync --no-perms --chmod=ugo+r -a --exclude=autoserv* --safe-links --exclude=*.core /var/spool/crash /usr/local/autotest/results/default/login_MultipleSessions/sysinfo/iteration.1/var/spool'
05/10 13:49:53.351 DEBUG|             utils:0202| Running 'rm -rf /var/spool/crash/*'
05/10 13:49:53.362 DEBUG|             utils:0202| Running 'logger "autotest finished iteration /usr/local/autotest/results/default/login_MultipleSessions/sysinfo/iteration.1"'
05/10 13:49:53.372 DEBUG|              test:0395| after_iteration_hooks completed
05/10 13:49:53.374 WARNI|              test:0615| The test failed with the following exception
Traceback (most recent call last):
  File "/usr/local/autotest/common_lib/test.py", line 609, in _exec
    _call_test_function(self.execute, *p_args, **p_dargs)
  File "/usr/local/autotest/common_lib/test.py", line 823, in _call_test_function
    raise error.UnhandledTestFail(e)
UnhandledTestFail: Unhandled DBusException: org.chromium.SessionManagerInterface.NoUserNssDb: Can't create session.
Traceback (most recent call last):
  File "/usr/local/autotest/common_lib/test.py", line 817, in _call_test_function
    return func(*args, **dargs)
  File "/usr/local/autotest/common_lib/test.py", line 470, in execute
    dargs)
  File "/usr/local/autotest/common_lib/test.py", line 347, in _call_run_once_with_retry
    postprocess_profiled_run, args, dargs)
  File "/usr/local/autotest/common_lib/test.py", line 380, in _call_run_once
    self.run_once(*args, **dargs)
  File "/usr/local/autotest/tests/login_MultipleSessions/login_MultipleSessions.py", line 42, in run_once
    self.__start_session_for(expected_owner)
  File "/usr/local/autotest/tests/login_MultipleSessions/login_MultipleSessions.py", line 81, in __start_session_for
    if not self._session_manager.StartSession(user, ''):
  File "/usr/local/lib64/python2.7/site-packages/dbus/proxies.py", line 145, in __call__
    **keywords)
  File "/usr/local/lib64/python2.7/site-packages/dbus/connection.py", line 651, in call_blocking
    message, timeout)
DBusException: org.chromium.SessionManagerInterface.NoUserNssDb: Can't create session.