Quoting Mattia Rizzolo <mattia@debian.org>:
I reckon the way forward is to fix those two FTBFS in calibre.
If calibre gets removed from testing on 2020-02-16, the reason for non-migration of cssutils and removing depending packages from testing, e.g. gajim, vanishes. Will this work out due to britneys wisdom? Or should calibre better removed from testing before 2020-02-16, if problems are not fixed until then?