Verified this on a just upgraded Ubuntu 15.10 where installation fails with

    $ sudo apt-get install npm
    Reading package lists... Done
    Building dependency tree       
    Reading state information... Done
    Some packages could not be installed. This may mean that you have
    requested an impossible situation or if you are using the unstable
    distribution that some required packages have not yet been created
    or been moved out of Incoming.
    The following information may help to resolve the situation:

    The following packages have unmet dependencies:
     npm : Depends: nodejs but it is not going to be installed
           Depends: node-abbrev (>= 1.0.4) but it is not going to be installed
           Depends: node-ansi (>= 0.3.0-2) but it is not going to be installed
           Depends: node-ansi-color-table but it is not going to be installed
           Depends: node-archy but it is not going to be installed
           Depends: node-block-stream but it is not going to be installed
           Depends: node-fstream (>= 0.1.22) but it is not going to be installed
           Depends: node-fstream-ignore but it is not going to be installed
           Depends: node-github-url-from-git but it is not going to be installed
           Depends: node-glob (>= 3.1.21) but it is not going to be installed
           Depends: node-graceful-fs (>= 2.0.0) but it is not going to be installed
           Depends: node-inherits but it is not going to be installed
           Depends: node-ini (>= 1.1.0) but it is not going to be installed
           Depends: node-lockfile but it is not going to be installed
           Depends: node-lru-cache (>= 2.3.0) but it is not going to be installed
           Depends: node-minimatch (>= 0.2.11) but it is not going to be installed
           Depends: node-mkdirp (>= 0.3.3) but it is not going to be installed
           Depends: node-gyp (>= 0.10.9) but it is not going to be installed
           Depends: node-nopt (>= 3.0.1) but it is not going to be installed
           Depends: node-npmlog but it is not going to be installed
           Depends: node-once but it is not going to be installed
           Depends: node-osenv but it is not going to be installed
           Depends: node-read but it is not going to be installed
           Depends: node-read-package-json (>= 1.1.0) but it is not going to be installed
           Depends: node-request (>= 2.25.0) but it is not going to be installed
           Depends: node-retry but it is not going to be installed
           Depends: node-rimraf (>= 2.2.2) but it is not going to be installed
           Depends: node-semver (>= 2.1.0) but it is not going to be installed
           Depends: node-sha but it is not going to be installed
           Depends: node-slide but it is not going to be installed
           Depends: node-tar (>= 0.1.18) but it is not going to be installed
           Depends: node-underscore but it is not going to be installed
           Depends: node-which but it is not going to be installed
    E: Unable to correct problems, you have held broken packages.

The requested output:

    $ sudo apt-cache policy node-gyp
    node-gyp:
      Installed: (none)
      Candidate: 0.12.2+ds-1
      Version table:
         0.12.2+ds-1 0
            500 http://de.archive.ubuntu.com/ubuntu/ wily/universe amd64 Packages