Comment 1 for bug 2049222

This is an Ubuntu delta in plymouth, we use alternatives:

    - We use alternatives instead of plymouth-set-default-theme tool:
      + debian/plymouth-themes.{prerm,postinst}: ensure we select one default
        plymouth logo and text themes through alternatives even when we remove
        ubuntu-base ones.
      + debian/rules, debian/plymouth.{install,links), don't ship non
        non alternative-based theme policy files and tools.
      + update plymouth.README.Debian to tell to use update-alternative
        instead of set-default-theme
      + change debian/local/plymouth.hook to use update-alternative to get
        default theme instead of set-default-theme. Also, don't copy
        deleted files to initramfs.