Install Mysql client driver linux

First find the driver (something like /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21) :

 sudo find / libmysql*.* | grep libmysql

if not found, try to install it, and retry.

 sudo apt-get install libmysqlclient*

It is possible to register the filename found when you will create or select your Database in Gestinux. Copy it's name. You can also run the command line below, replacing the 2nd file by the driver path found before.

 sudo ln -s /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21  /usr/lib/mysqlclient.so