This is happening on a Qubes debian-9 VM for me. So this could be a Debian issue. By extension, Whonix would be affected as well.
user@debian-9:~$ sudo apt-get dist-upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages will be REMOVED:
enigmail
The following packages will be upgraded:
ghostscript icedove libgs9 libgs9-common libmarkdown2 lightning thunderbird
7 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
Need to get 44.5 MB of archives.
After this operation, 28.4 MB of additional disk space will be used.
Do you want to continue? [Y/n]