Hi phobbs!

I noticed that cros_make_image_bootable is failing. There are a whole bunch of odd error messages that make me think it might be related to the builder having issues. 
If this is not an infra issue, please assign it back to me so I can find someone to investigate this failure. 

Log:
mount: /dev/loop3: can't read superblock
ERROR   : Thu Apr 21 06:50:13 PDT 2016
ERROR   :  PGID  PPID   PID     ELAPSED     TIME %CPU COMMAND
ERROR   : Arguments of 1707:  '--arch=amd64' '--to=/mnt/host/source/src/build/images/cyan/R52-8222.0.0/chromiumos_base_image.bin' '--from=/mnt/host/source/src/build/images/cyan/R52-8222.0.0/rootfs_dir/boot' '--vmlinuz=/mnt/host/source/src/build/images/cyan/R52-8222.0.0/rootfs_dir/boot/vmlinuz' '--to_offset=127926272' '--to_size=16777216' '--kernel_partition='/mnt/host/source/src/build/images/cyan/R52-8222.0.0/vmlinuz.image'' '--install_syslinux'
ERROR   : Backtrace:  (most recent call is last)
ERROR   :  update_bootloaders.sh:197:main(), called: die_err_trap  
ERROR   : 
ERROR   : Command failed:
ERROR   :   Command 'sudo mount -o ro "${ESP_DEV}" "${ESP_FS_DIR}"' exited with nonzero code: 32
umount: /tmp/esp.ZITuZp: not mounted
WARNING : Initial unmount failed. Possibly crosbug.com/23443. Retrying
umount: /tmp/esp.ZITuZp: not mounted
INFO    : Unmounting image from /mnt/host/source/src/build/images/cyan/R52-8222.0.0/stateful_dir and /mnt/host/source/src/build/images/cyan/R52-8222.0.0/rootfs_dir
Cleaning up /usr/local symlinks for /mnt/host/source/src/build/images/cyan/R52-8222.0.0/stateful_dir/dev_image
ERROR   : Thu Apr 21 06:50:24 PDT 2016
ERROR   :  PGID  PPID   PID     ELAPSED     TIME %CPU COMMAND
ERROR   : Arguments of 32459:  '/mnt/host/source/src/build/images/cyan/R52-8222.0.0' 'chromiumos_base_image.bin' '--adjust_part='
ERROR   : Backtrace:  (most recent call is last)
ERROR   :  cros_make_image_bootable:427:main(), called: make_image_bootable '/mnt/host/source/src/build/images/cyan/R52-8222.0.0/chromiumos_base_image.bin' 
ERROR   :  cros_make_image_bootable:1:make_image_bootable(), called: die 'cros_make_image_bootable failed.' 
ERROR   : 
ERROR   : Error was:
ERROR   :   cros_make_image_bootable failed.
06:50:25: ERROR: 
return code: 1; command: /b/cbuild/internal_master/chromite/bin/cros_sdk 'PARALLEL_EMERGE_STATUS_FILE=/tmp/tmpYJlXLi' 'USE=-cros-debug chrome_internal afdo_use' 'FEATURES=separatedebug' 'CHROME_ORIGIN=LOCAL_SOURCE' -- ./build_image '--board=cyan' --replace '--version=8222.0.0' base test
cwd=/b/cbuild/internal_master, extra env={'PARALLEL_EMERGE_STATUS_FILE': '/tmp/tmpYJlXLi', 'USE': '-cros-debug chrome_internal afdo_use', 'FEATURES': 'separatedebug', 'CHROME_ORIGIN': 'LOCAL_SOURCE'}
Build: https://uberchromegw.corp.google.com/i/chromeos/builders/strago-release-group/builds/1101