Preparation for install python-stem, which is unfortunately only available from Debian testing, not stable. Added Debian testing repository to /etc/apt/sources.list and configured apt pinning in /etc/apt/preferences.d/50_whonix. #60
Merge remote-tracking branch 'origin/master'
apply our apt preferences.d settings (apt pinning) while building Whonix from source code and while updating Whonix from source code