grunt-paladin was failing to build chromeos-firmware-grunt for several builds in a row, possibly due to a version bump as in  crbug.com/859556  - however, it seems that later builds are now succeeding.

Affected builds:
https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8927037755004870464
https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8927027669670510016
https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8927020634001478384
https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8927014313243209936




Example BuildPackages output from a failed build:


=== Start output for job chromeos-firmware-grunt-0.0.1-r110 (0m3.6s) ===
chromeos-firmware-grunt-0.0.1-r110: >>> Emerging (1 of 1) chromeos-base/chromeos-firmware-grunt-0.0.1-r110::grunt-private for /build/grunt/
chromeos-firmware-grunt-0.0.1-r110:  * Aleena.11031.44.0.tbz2 SHA256 SHA512 WHIRLPOOL size ;-) ...           [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Aleena_EC.11031.44.0.tbz2 SHA256 SHA512 WHIRLPOOL size ;-) ...        [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Careena.11031.34.0.tbz2 SHA256 SHA512 WHIRLPOOL size ;-) ...          [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Careena.11031.44.0.tbz2 SHA256 SHA512 WHIRLPOOL size ;-) ...          [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Careena_EC.11031.34.0.tbz2 SHA256 SHA512 WHIRLPOOL size ;-) ...       [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Delan.11031.44.0.tbz2 SHA256 SHA512 WHIRLPOOL size ;-) ...            [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Delan_EC.11031.44.0.tbz2 SHA256 SHA512 WHIRLPOOL size ;-) ...         [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Grunt.11031.44.0.tbz2 SHA256 SHA512 WHIRLPOOL size ;-) ...            [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Grunt_EC.11031.44.0.tbz2 SHA256 SHA512 WHIRLPOOL size ;-) ...         [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Liara.11031.44.0.tbz2 SHA256 SHA512 WHIRLPOOL size ;-) ...            [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Liara_EC.11031.44.0.tbz2 SHA256 SHA512 WHIRLPOOL size ;-) ...         [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Running stacked hooks for pre_pkg_setup
chromeos-firmware-grunt-0.0.1-r110:  *    sysroot_build_bin_dir ...
chromeos-firmware-grunt-0.0.1-r110:  [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Running stacked hooks for post_pkg_setup
chromeos-firmware-grunt-0.0.1-r110:  *    python_eclass_hack ...
chromeos-firmware-grunt-0.0.1-r110:  [ ok ]
chromeos-firmware-grunt-0.0.1-r110:  * Running stacked hooks for pre_src_unpack
chromeos-firmware-grunt-0.0.1-r110:  *    python_multilib_setup ...
chromeos-firmware-grunt-0.0.1-r110:  [ ok ]
chromeos-firmware-grunt-0.0.1-r110: >>> Unpacking source...
chromeos-firmware-grunt-0.0.1-r110: Cloning into '/build/grunt/tmp/portage/chromeos-base/chromeos-firmware-grunt-0.0.1-r110/work/chromeos-firmware-grunt-0.0.1'...
chromeos-firmware-grunt-0.0.1-r110: done.
chromeos-firmware-grunt-0.0.1-r110: >>> Source unpacked in /build/grunt/tmp/portage/chromeos-base/chromeos-firmware-grunt-0.0.1-r110/work
chromeos-firmware-grunt-0.0.1-r110:  * Running stacked hooks for post_src_unpack
chromeos-firmware-grunt-0.0.1-r110:  *    asan_init ...
chromeos-firmware-grunt-0.0.1-r110:  [ ok ]
chromeos-firmware-grunt-0.0.1-r110: >>> Preparing source in /build/grunt/tmp/portage/chromeos-base/chromeos-firmware-grunt-0.0.1-r110/work/chromeos-firmware-grunt-0.0.1 ...
chromeos-firmware-grunt-0.0.1-r110: >>> Source prepared.
chromeos-firmware-grunt-0.0.1-r110: >>> Configuring source in /build/grunt/tmp/portage/chromeos-base/chromeos-firmware-grunt-0.0.1-r110/work/chromeos-firmware-grunt-0.0.1 ...
chromeos-firmware-grunt-0.0.1-r110: >>> Source configured.
chromeos-firmware-grunt-0.0.1-r110: >>> Compiling source in /build/grunt/tmp/portage/chromeos-base/chromeos-firmware-grunt-0.0.1-r110/work/chromeos-firmware-grunt-0.0.1 ...
chromeos-firmware-grunt-0.0.1-r110:  * Build grunt firmware updater to chromeos-firmwareupdate:  -i /build/grunt/tmp/portage/chromeos-base/chromeos-firmware-grunt-0.0.1-r110/distdir -c /build/grunt/usr/share/chromeos-config/yaml/config.yaml
chromeos-firmware-grunt-0.0.1-r110: Traceback (most recent call last):
chromeos-firmware-grunt-0.0.1-r110:   File "./pack_firmware.py", line 993, in <module>
chromeos-firmware-grunt-0.0.1-r110:     main(sys.argv)
chromeos-firmware-grunt-0.0.1-r110:   File "./pack_firmware.py", line 990, in main
chromeos-firmware-grunt-0.0.1-r110:     packer.Start(argv[1:])
chromeos-firmware-grunt-0.0.1-r110:   File "./pack_firmware.py", line 962, in Start
chromeos-firmware-grunt-0.0.1-r110:     firmware_info[model], args, model_details)
chromeos-firmware-grunt-0.0.1-r110:   File "./pack_firmware.py", line 835, in _GenerateOneModel
chromeos-firmware-grunt-0.0.1-r110:     dirname)
chromeos-firmware-grunt-0.0.1-r110:   File "./pack_firmware.py", line 792, in _ExtractFile
chromeos-firmware-grunt-0.0.1-r110:     os.path.join(self._args.imagedir, fname), dirname, suffix)
chromeos-firmware-grunt-0.0.1-r110:   File "./pack_firmware.py", line 622, in _UntarFile
chromeos-firmware-grunt-0.0.1-r110:     with tarfile.open(pathname) as tar:
chromeos-firmware-grunt-0.0.1-r110:   File "/usr/lib64/python2.7/tarfile.py", line 1667, in open
chromeos-firmware-grunt-0.0.1-r110:     return func(name, "r", fileobj, **kwargs)
chromeos-firmware-grunt-0.0.1-r110:   File "/usr/lib64/python2.7/tarfile.py", line 1732, in gzopen
chromeos-firmware-grunt-0.0.1-r110:     fileobj = gzip.GzipFile(name, mode, compresslevel, fileobj)
chromeos-firmware-grunt-0.0.1-r110:   File "/usr/lib64/python2.7/gzip.py", line 94, in __init__
chromeos-firmware-grunt-0.0.1-r110:     fileobj = self.myfileobj = __builtin__.open(filename, mode or 'rb')
chromeos-firmware-grunt-0.0.1-r110: IOError: [Errno 2] No such file or directory: '/build/grunt/tmp/portage/chromeos-base/chromeos-firmware-grunt-0.0.1-r110/distdir/Aleena.11031.43.0.tbz2'
chromeos-firmware-grunt-0.0.1-r110:  * ERROR: chromeos-base/chromeos-firmware-grunt-0.0.1-r110::grunt-private failed (compile phase):
chromeos-firmware-grunt-0.0.1-r110:  *   Cannot pack firmware updater.
chromeos-firmware-grunt-0.0.1-r110:  * 
chromeos-firmware-grunt-0.0.1-r110:  * Call stack:
chromeos-firmware-grunt-0.0.1-r110:  *     ebuild.sh, line  133:  Called src_compile
chromeos-firmware-grunt-0.0.1-r110:  *   environment, line 3733:  Called cros-firmware_src_compile
chromeos-firmware-grunt-0.0.1-r110:  *   environment, line  967:  Called die
chromeos-firmware-grunt-0.0.1-r110:  * The specific snippet of code:
chromeos-firmware-grunt-0.0.1-r110:  *           ./pack_firmware.py "${image_cmd[@]}" "${ext_cmd[@]}" -o "${output}" || die "Cannot pack firmware updater.";