sudo snappy update
Installing ubuntu-core (101)
Syncing boot files
Starting download of ubuntu-core
166.33 KB / 166.33 KB [================================================] 100.00 % 24.00 KB/s 
Done
error from system-image-cli: http://system-image.ubuntu.com/ubuntu-core/15.04/edge/generic_amd64/version-100.tar.xz.asc (Empty reply from server)