$ sudo ubuntu-device-flash --verbose core --output=snappy.img --developer-mode --channel=stable 15.04
Determining oem configuration
Starting download of generic-amd64
40.93 KB / 40.93 KB [=======================================================================================================] 100.00 % 332.61 KB/s 
Done
operation not supported
2015/06/09 09:52:37 Warning: failed to remove /tmp/oem071319702/oem/generic-amd64/1.1.1: %!s(<nil>)
2015-06-09 07:52:37 ERROR snappy logger.go:199 generic-amd64 failed to install: unpack /tmp/generic-amd64379314941 to /tmp/oem071319702/oem/generic-amd64/1.1.1 failed with exit status 1
generic-amd64 failed to install: unpack /tmp/generic-amd64379314941 to /tmp/oem071319702/oem/generic-amd64/1.1.1 failed with exit status 1