[DRE-maint] Bug#948982: schleuder: fails to handle mails in different charsets depending on the environment

[Georg Faerber]

Package: schleuder
Version: 3.4.1-1
Forwarded: https://0xacab.org/schleuder/schleuder/issues/409 
Tags: fixed-upstream

Currently, depending on the environment, which differs for example
between Postfix and Exim, Schleuder may run into a fatal error due to
"invalid byte sequence in US-ASCII" if handling mails with different
charsets.

A fix addressing this issue was released upstream: default to ASCII-8BIT
encoding for external data in any case. This change ensures, that
Schleuder is able to handle mails with different charsets, regardless
via which MTA, for example Postfix or Exim, it was invoked.