I think the reason is that calibre writes files to /usr/lib/calibre on
startup that debian doesn't know about. E.g. in a fresh install:
ls -l /usr/lib/calibre/calibre
-rw-r--r-- 1 root root 10072 Feb 8 09:41 constants.py
-rw-r--r-- 1 root root 15317 Feb 8 09:41 debug.py
-rw-r--r-- 1 root root 2988 Feb 8 09:41 gui_launch.py
...
and after starting calibre, it creates .pyc files:
-rw-r--r-- 1 root root 10072 Feb 8 09:41 constants.py
-rw-r--r-- 1 root root 10520 May 9 03:54 constants.pyc
-rw-r--r-- 1 root root 15317 Feb 8 09:41 debug.py
-rw-r--r-- 1 root root 2988 Feb 8 09:41 gui_launch.py
-rw-r--r-- 1 root root 4124 May 9 03:54 gui_launch.pyc
...
The original problem is that calibre at one point generated .pyc files
in calibre/regex that dpkg didn't know anything about, and thus dpkg was
unable to remove them.
--
The choice of a Deliantra, the free code+content MORPG
-----==- _GNU_ http://www.deliantra.net
----==-- _ generation
---==---(_)__ __ ____ __ Marc Lehmann
--==---/ / _ \/ // /\ \/ / schm...@schmorp.de
-=====/_/_//_/\_,_/ /_/\_\
