snapcraft 
Loaded local plugin for gschema
Skipping pull snap-preload-shim (already ran)
Preparing to pull unity8 
Hit http://ppa.launchpad.net/ci-train-ppa-service/stable-phone-overlay/ubuntu xenial InRelease                                                                                                                                                                                 
Hit http://archive.ubuntu.com/ubuntu xenial InRelease                                                                                                                                                                                                                          
Hit http://archive.ubuntu.com/ubuntu xenial-updates InRelease                                                                                                                                                                                                                  
Fetched 0 B in 0s (0 B/s)                                                                                                                                                                                                                                                      
E:Unable to correct problems, you have held broken packages.