Comment 2 for bug 43470

While it IS a bug that mozilla-thinderbird-typeaheadfind contains /tmp, I don't think it can be responsible for your breakage. As I understand it, dpkg will never change the permissions on a directory once it exists on the filesystem, so there'd have to be something pretty interesting going on for /tmp to disappear completely during upgrade before mozilla-thinderbird-typeaheadfind gets installed.

Given that base-files is an Essential package, I just don't see how this could realistically happen.

Scott, do you have any light to shed on this? (the breakage, not the bug with the package shipping the directory)