Mark as junk in Evolution, train SpamAssassin on server

Evolution has a feature for marking e-mail as junk. This will set an IMAP keyword “Junk” on those messages. On my mail server I run Dovecot as IMAP server and Spamassassin through Amavis to filter spam. How could I get Spamassassin to learn that all e-mails marked as junk in Evolution are spam? With a shell script, of course. I currently run it as root but maybe it is possible to give the amavis user permissions to read my Maildir…

#!/bin/sh

if [ `whoami` != 'root' ]; then
  exec sudo $0 $@
fi

find ~david/Maildir -name dovecot-keywords | (
while read keywords; do

  DIR=`dirname $keywords`
  #echo $DIR >&2
  # XXX only supports 10 keywords
  CHAR=`awk '$2 == "Junk" { print $1; quit;  }' $keywords |
    tr '0-9' 'a-j'`

  if [ "$CHAR" ]; then
    find $DIR/cur $DIR/new -regex "[^,]*,[^,]*$CHAR.*" |
      xargs sa-learn --dbpath /var/lib/amavis/.spamassassin/ --spam
  fi

done
)
/etc/init.d/spamassassin reload

Helpful pages: Maildir format used by Dovecot, Spamassassin with amavis: Tips and tricks.