I attempted to perform a dist-upgrade today and the result would have been the removal of
network-manager-pptp and
network-manager-pptp-gnome. There were 75 packages to be upgraded, including LibreOffice, so I didn't feel like holding off.
I did a little bit of research and discovered that
network-manager-pptp depended on a particular version of
ppp, which was to be upgraded to version 2.4.7. This explained why
network-manager-pptp was going to be removed.
network-manager-pptp-gnome relies on
network-manager-pptp, which explains why
network-manager-pptp-gnome was going to be removed.
I put
ppp on hold:
sudo apt-mark hold ppp
I then commenced to perform the dist-upgrade, without any packages being removed, and then unheld
ppp:
sudo apt-mark unhold ppp
Sweet!