I've been having issues upgrading a standard Devuan Jessie install to
Ascii. During upgrade, the task-xfce4-desktop package gets uninstalled and
can't be installed afterwards due to dependency problems.

Jessie has tasksel=3.33+devuan1.0 and Ascii has tasksel=3.33+devuan0.3
which is preventing task-xfce4-desktop from being installed in Ascii. This
is also causing a number of xfce4-* and other packages to be marked as not
required and removable with apt-get autoremove.

# apt-cache policy tasksel
tasksel:
  Installed: 3.33+devuan1.0
  Candidate: 3.33+devuan1.0
  Version table:
 *** 3.33+devuan1.0 100
        100 /var/lib/dpkg/status
     3.33+devuan0.3 500
        500 http://auto.mirror.devuan.org/merged ascii/main amd64 Packages

# apt-cache policy task-xfce-desktop
task-xfce-desktop:
  Installed: (none)
  Candidate: 3.33+devuan0.3
  Version table:
     3.33+devuan0.3 500
        500 http://auto.mirror.devuan.org/merged ascii/main amd64 Packages

# apt-get install task-xfce-desktop
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:
 task-xfce-desktop : Depends: tasksel (= 3.33+devuan0.3) but 3.33+devuan1.0
is to be installed
                     Depends: xfce4 but it is not going to be installed
                     Recommends: xfce4-mixer but it is not installable
E: Unable to correct problems, you have held broken packages.

-- Tom