It happened on this build:

    https://uberchromegw.corp.google.com/i/chromeos/builders/lumpy-chrome-pfq/builds/9218

In the security_SandboxedServices.DEBUG logs for the run:

    https://pantheon.corp.google.com/storage/browser/chromeos-autotest-results/80837963-chromeos-test/

This is the relevant excerpt:

    CmdError: Command <awk '$1 ~ "^(Pid|CapInh|CapPrm|CapEff|CapBnd|Seccomp):" {printf "%s ", $NF; if ($1 == "Seccomp:") printf "\n"}' /proc/[1-9]*/status> failed, rc=2, Command returned non-zero exit status
    * Command: 
        awk '$1 ~ "^(Pid|CapInh|CapPrm|CapEff|CapBnd|Seccomp):" {printf "%s ",
        $NF; if ($1 == "Seccomp:") printf "\n"}' /proc/[1-9]*/status
    Exit status: 2
    Duration: 0.00886988639832
    stdout:
    1 0000000000000000 0000001fffffffff 0000001fffffffff 0000001fffffffff 0 
    [...]
    17635 0000000000000000 0000001fffffffff 0000001fffffffff 0000001fffffffff 0
    stderr:
    awk: cannot open /proc/17636/status (No such file or directory)

Looks like a simple race due to a process ending after the filename has been matched but before the path is opened.