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]