Comment 8 for bug 352118

[quote]
So one workaround is to simply edit the file:

  /usr/share/dbus-1/system-services/fi.epitest.hostap.WPASupplicant.service

and remove the -s from from the exec line. This will prevent all
wpa_supplicant messages hitting the syslog, and that is what upstream
wpa_supplicant binaries will do --- the -s option was added by
debian/patches/11_syslog.patch.
[/quote]
that workaround worked for me.
quoting Ted in http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=539915