I ran into this problem as well and I found this way to get spamassassin installed.
While installing spamassassin using apt-get install; the user-id debian-spamd is created and given the /bin/sh - shell. After I changed the shell to /bin/bash and issued the "apt-get install spamassassin" again; the package(s) got installed normally without an error.
sa-compile throws an error when started as user debian-spamd and using the "sh" - shell and this binary is started during the installation, hence the installation failure...
If the installation script creates the user with the "bash" - shell it might solve this broken installation.
-- Met vriendelijke groet, kind regards, Fred de Brouwer
