A bunch of recent -release builds fail in TestSimpleChromeWorkflow:

daisy-release: https://logs.chromium.org/logs/chromeos/buildbucket/cr-buildbucket.appspot.com/8924846644289184960/+/steps/TestSimpleChromeWorkflow/0/stdout
peppy-release: https://logs.chromium.org/logs/chromeos/buildbucket/cr-buildbucket.appspot.com/8924846583288327136/+/steps/TestSimpleChromeWorkflow/0/stdout
clapper-release: https://logs.chromium.org/logs/chromeos/buildbucket/cr-buildbucket.appspot.com/8924846647462527392/+/steps/TestSimpleChromeWorkflow/0/stdout
peach_pit-release: https://logs.chromium.org/logs/chromeos/buildbucket/cr-buildbucket.appspot.com/8924846584395417200/+/steps/TestSimpleChromeWorkflow/0/stdout

Killing compiler proxy.
  compiler proxy status: http://127.0.0.1:8088 quit!
  21:06:39: INFO: RunCommand: cros --log-level debug --cache-dir /b/swarming/w/ir/tmp/t/cbuildbot-tmpeKk8nM/chrome-sdk-cacheXpcWoI/cache chrome-sdk --board peach_pit --cwd /b/swarming/w/ir/cache/cbuild/repository/.cache/distfiles/target-master/chrome-src-internal/src --sdk-path /b/swarming/w/ir/cache/cbuild/repository/buildbot_archive/peach_pit-release/R73-11549.0.0 --nogn-gen --nostart-goma --gomadir /b/swarming/w/ir/cache/goma/client --internal --chrome-src /b/swarming/w/ir/cache/cbuild/repository/.cache/distfiles/target-master/chrome-src-internal/src -- /b/swarming/w/ir/cache/cbuild/repository/chromite/bin/deploy_chrome --build-dir /b/swarming/w/ir/cache/cbuild/repository/.cache/distfiles/target-master/chrome-src-internal/src/out_peach_pit/Release --staging-only --staging-dir /b/swarming/w/ir/tmp/t/cbuildbot-tmpeKk8nM/chrome-sdk-stageBIiJfD in /b/swarming/w/ir/cache/cbuild/repository
  21:06:39: DEBUG: Configured cache_dir to '/b/swarming/w/ir/tmp/t/cbuildbot-tmpeKk8nM/chrome-sdk-cacheXpcWoI/cache'
  21:06:40: DEBUG: RunCommand: /b/swarming/w/ir/tmp/t/cbuildbot-tmpeKk8nM/chrome-sdk-cacheXpcWoI/cache/common/gsutil_4.33.tar.gz/gsutil/gsutil -o 'Boto:num_retries=10' ls gs://chromeos-authentication-bucket/
  gs://chromeos-authentication-bucket/README.txt
  21:06:41: WARNING: app-emulation/qemu not found.
  21:06:41: WARNING: sys-firmware/seabios not found.
  21:06:41: WARNING: Could not create Seabios firmware links.
  21:06:41: INFO: Removing symbol_level = 2 from gn args, use --gn-extra-args to specify a non default value.
  21:06:41: INFO: Staging flags taken from USE in environment: highdpi
  21:06:43: WARNING: app-emulation/qemu not found.
  21:06:43: WARNING: sys-firmware/seabios not found.
  21:06:43: WARNING: Could not create Seabios firmware links.
  21:06:45: ERROR: Traceback (most recent call last):
    File "/b/swarming/w/ir/cache/cbuild/repository/chromite/cbuildbot/stages/generic_stages.py", line 723, in Run
      self.PerformStage()
    File "/b/swarming/w/ir/cache/cbuild/repository/chromite/cbuildbot/stages/chrome_stages.py", line 340, in PerformStage
      self._VMTest(sdk_cmd)
    File "/b/swarming/w/ir/cache/cbuild/repository/chromite/cbuildbot/stages/chrome_stages.py", line 309, in _VMTest
      constants.VM_IMAGE_BIN))
    File "/b/swarming/w/ir/cache/cbuild/repository/chromite/cbuildbot/commands.py", line 3134, in VMTest
      assert image_path and os.path.exists(image_path)
  AssertionError

This seems to be new in R73-11549.0.0, R73-11547.0.0 was fine. Both use the same Chrome 73.0.3664.0.