R71 grunt-release builder has failed the last two builds, both in the CanaryCompletion stage.  The error messages sound similar to  crbug.com/791061 .

R71-11151.123.0:
https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?id=3372227
Failed in CanaryCompletion:
grunt-release: The Signing stage failed: ChromeOS-recovery-R71-11151.123.0-grunt.instructions.json"
----
01:38:15: INFO: Updating status with message grunt-release: The Signing stage failed: ChromeOS-recovery-R71-11151.123.0-grunt.instructions.json in https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8924110539937460320
01:38:15: INFO: Updating manifest-versions checkout.
01:39:52: INFO: Pushing to branch (_RemoteRef(remote='origin', ref='refs/heads/master', project_name=None)) with message: Automatic checkin: status=fail build_version 11151.123.0 for grunt-release 
01:40:01: ERROR: Failed to update the status for grunt-release during remote command: return code: 1; command: git push origin temp_auto_checkin_branch:refs/heads/master
remote: 
remote: Processing changes: refs: 3        
remote: Processing changes: refs: 3, done            
To https://chrome-internal.googlesource.com/chromeos/manifest-versions
 ! [remote rejected]         temp_auto_checkin_branch -> master (failed to lock)
error: failed to push some refs to 'https://chrome-internal.googlesource.com/chromeos/manifest-versions'
[W git.go:283] Transient error string identified in STDERR: " ! [remote rejected]         temp_auto_checkin_branch -> master (failed to lock)\n"
[W git.go:294] Retrying after 3s (rc=1): transient error string encountered
To https://chrome-internal.googlesource.com/chromeos/manifest-versions
 ! [rejected]                temp_auto_checkin_branch -> master (fetch first)
error: failed to push some refs to 'https://chrome-internal.googlesource.com/chromeos/manifest-versions'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.
[W git.go:317] Command completed with rc 1 after 1 transient failure(s).



R71-11151.126.0:
https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?id=3372227
StatusUpdateException
----
03:45:48: INFO: Updating manifest-versions checkout.
03:47:19: INFO: Pushing to branch (_RemoteRef(remote='origin', ref='refs/heads/master', project_name=None)) with message: Automatic checkin: status=pass build_version 11151.126.0 for grunt-release 
03:47:19: ERROR: Failed to update the status for grunt-release during remote command: return code: 1; command: git push origin temp_auto_checkin_branch:refs/heads/master
To https://chrome-internal.googlesource.com/chromeos/manifest-versions
 ! [rejected]                temp_auto_checkin_branch -> master (fetch first)
error: failed to push some refs to 'https://chrome-internal.googlesource.com/chromeos/manifest-versions'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.