Migrate WhisperBack from python-gnupginterface to python-gnupg
Tails Greeter currently uses GnuPGInterface whose not maintained anymore. It should be ported to python-gnupg which now seems to include all the features we need and is packaged in jessie for python3.
Related issues
- Is duplicate of #7755 (closed)
Original created by @alant on 7805 (Redmine)