$ sudo /snap/bin/ubuntu-device-flash --verbose core 16 -o /home/ted/xenial_core_amd64.img --gadget=pc --kernel=pc-kernel --os=ubuntu-core --size=8
Determining gadget configuration
 164.00 KB / 164.00 KB [======================================================================================================] 100.00% 440.83 KB/s 0
Partitioning...
issues while partitioning: exit status 1