Comment 2 for bug 213482

The other logs from /var/log/dist-upgrade would indeed be useful.

As you noted the relevant point seems to be:

 dpkg: libsasl2: dependency problems, but removing anyway as you request:
 slapd depends on libsasl2 (>= 2.1.19.dfsg1); however:
  Package libsasl2 is to be removed.

I tried to investigate the dependencies of libsasl2:
sudo apt-cache showpkg libsasl2
Package: libsasl2
Versions:

Reverse Depends:
  libsasl2-2,libsasl2
Dependencies:
Provides:
Reverse Provides:

$ sudo apt-cache depends libsasl2-2
libsasl2-2
  Depends: libc6
  Depends: libdb4.2
 |Depends: libsasl2-modules
 |Depends: libsasl2-modules-sql
 |Depends: libsasl2-modules-gssapi-heimdal
  Depends: <libsasl2-modules-kerberos-heimdal>
  Conflicts: postfix
  Conflicts: <libsasl2-gssapi-mit>
  Conflicts: <libsasl2-krb4-mit>
  Replaces: <libsasl2>