ERROR in ChromeLauncher taskkill command prevents logging summary results

[harper84]

This is potentially out of scope for lighthouse-batch, but at the end of a successful Lighthouse run (after the report JSON has been generated), sometimes ChromeLauncher is unable to terminate the Chrome task because one or more of its children have already been terminated, e.g.

status Generating results...
Printer json output written to output.json
ChromeLauncher Killing Chrome instance 2720
ChromeLauncher:warn Chrome could not be killed Command failed: taskkill /pid 2720 /T /F
ERROR: The process with PID 5676 (child process of PID 2720) could not be terminated.
Reason: There is no running instance of the task.

the value of outcome (index.js line 56) is now non-zero (as there is an error on the command line), even though the bit we care about (the report generation step) actually completed.

Expecting lighthouse-batch to be able to parse and understand the error output is probably asking a bit much(!), but would it be possible to include an error override flag in the lighthouse-batch parameters to enable best-effort processing in updateSummary (index.js line 172) in edge-cases like this, rather than just recording the error message against blank summary values?

(as an aside, the underlying problem seems to be that Lighthouse CLI reports failure to kill a child process as an ERROR, even though a failure to kill the parent process itself is merely a WARNING. I'll be raising this issue against Lighthouse CLI separately!)