lumpy-pre-flight-branch failed last 2 times, https://uberchromegw.corp.google.com/i/chromiumos.release/builders/lumpy-pre-flight-branch%20release-R50-7978.B/builds/138, 

log:
chromite-0.0.2-r2279: 14:16:40: ERROR: Image signing timed out
chromite-0.0.2-r2279: STEP_TEXT: Image signing timed out.
chromite-0.0.2-r2279: ok
chromite-0.0.2-r2279: 
chromite-0.0.2-r2279: ======================================================================
chromite-0.0.2-r2279: ERROR: [chromite.cbuildbot.stages.release_stages_unittest] PaygenStageTest.testPerformStageNoChannels
chromite-0.0.2-r2279: Test that PaygenStage works when signing works.
chromite-0.0.2-r2279: ----------------------------------------------------------------------
chromite-0.0.2-r2279: Traceback (most recent call last):
chromite-0.0.2-r2279:   File "/mnt/host/source/chromite/lib/timeout_util.py", line 158, in TimeoutWrapper
chromite-0.0.2-r2279:     func(*args, **kwargs)
chromite-0.0.2-r2279:   File "/mnt/host/source/chromite/cbuildbot/stages/release_stages_unittest.py", line 337, in testPerformStageNoChannels
chromite-0.0.2-r2279:     stage.board_runattrs.SetParallel('signed_images_ready', [])
chromite-0.0.2-r2279:   File "/mnt/host/source/chromite/cbuildbot/cbuildbot_run.py", line 525, in SetParallel
chromite-0.0.2-r2279:     *args, **kwargs)
chromite-0.0.2-r2279:   File "/mnt/host/source/chromite/cbuildbot/cbuildbot_run.py", line 290, in SetBoardParallel
chromite-0.0.2-r2279:     raise ParallelAttributeError(attr, board=board, target=target)
chromite-0.0.2-r2279: ParallelAttributeError: No such board-specific parallel run attribute 'signed_images_ready' for x86-alex_he/x86-alex_he-release