System unbootable after full encyption install with non US keyboard

[Ric Flomag]

Linux Mint 17.3 64 bit Cinnamon Edition

Example case :
 * Camilo's laptop has a French (or whatever non-US) keyboard
 * They install Mint 17.3 with full disc encryption
 * Installation finishes, the laptop is rebooted but won't boot because of a wrong cryptsetup password due to a keyboard layout mismatch.

How to reproduce :
 * Choose a password for full disc encryption that includes any of the following : a,q,w,z,m, numbers, sign or accentuated characters.

Reason why :
 * Keyboard layout defaults to US, whatever language is selected at the first step of the Ubiquity installation process.
 * Users have no information whatsoever that the keyboard layout does not match their keyboard

Expected :
 * option 1 : The keyboard layout selection step is moved from when it is now (after time zone selection) to the beginning (before full disc encryption password setting)
 * option 2 : keyboard layout is set accordingly to the first step (language setting)
 * option 3 : reproduce the Ubuntu install flow : users select their language at the very beginning of the boot process from the live media and the keyboard layout is set accordingly.

Note that only the first option makes sure that the keyboard layout is OK in all cases : for example, if the user wants to install Mint in Spanish using a laptop with a French Keyboard.

[Ric Flomag (ricflomag)]

Possibly related bug (not very clear to me) : #1327728