$ sudo ubuntu-device-flash --verbose core --output=/tmp/snappy.img  --developer-mode --channel=ubuntu-core/devel-proposed --size 3 -oem beagleblack.canonical --install=webdm.canonical
Determining oem configuration
Fetching information from server...
Downloading and setting up...
Download finished for /home/elopio/.cache/ubuntuimages/ubuntu-core/devel-proposed/generic_amd64/version-400.tar.xz
37.85 MB / 37.85 MB [======================================] 100.00 % 1.51 MB/s 
Download finished for /home/elopio/.cache/ubuntuimages/pool/ubuntu-6a25584850f117a212aa6f72d9273df9d1f9cc620628af279c5c72df2eb420db.tar.xz
75.48 MB / 75.48 MB [======================================] 100.00 % 1.87 MB/s 
Searching for hardware.yaml in device part
Download finished for /home/elopio/.cache/ubuntuimages/pool/device-5195bb0c29a5c255ae54ff9b3374e39d80f2c93a8b2670defd3028b8bf144406.tar.xz
Partitioning...
Mapping...
Formatting...
Mapping...
Mounting...
Provisioning...
Installing webdm.canonical
2015-04-17 15:22:34 ERROR snappy logger.go:199 snappy package not found
Unmounting...
Unmapping...
snappy package not found