#Linux Mint 18.2 how to install gajim .16.9 so you can use OMEMO encryption:
sudo apt-get install python-axolotl python-nbxmpp
wget https://gajim.org/downloads/0.16/gajim-0.16.9.tar.gz
tar -zxvf gajim-0.16.9.tar.gz
cd gajim-0.16.9
./autogen.sh ;make;sudo make install
#if you get this error you need to get a newer python-nbxmpp from here:
gajim
Gajim needs python-nbxmpp >= 0.6.1 to run. Quiting...........