Local keyboard layout is selected only after entering full system encryption key

When choosing to do a full system encryption while installing Ubuntu, the user is asked to set the encryption key *before* they have the opportunity to select the correct keymap. E.g. I use a german keyboard but when I enter my desired encryption key the keymap is still in "US" mode, so some letters and symbols are on different positions on the keyboard. This is confusing because the user has to enter the desired key in "US" mode and has to find out where the right symbols are located in order to get the "correct" encryption key afterwards. Not using these keys is not a great solution, because not being able to use most symbols sacrifices the ability to enter a strong encryption key.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: ubiquity (not installed)
ProcVersionSignature: Ubuntu 4.2.0-16.19-generic 4.2.3
Uname: Linux 4.2.0-16-generic x86_64
ApportVersion: 2.19.1-0ubuntu3
Architecture: amd64
CurrentDesktop: MATE
Date: Fri Dec 25 18:38:02 2015
InstallationDate: Installed on 2015-12-25 (0 days ago)
InstallationMedia: Ubuntu-MATE 15.10 "Wily Werewolf" - Release amd64 (20151021)
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)