Uibiquity crashes when installing on LUKS-encrypted partition

[Sebastian Pochert]

The installer crashed and told me to report a bug using ubuntu-bug ubiquity so that's what I'm doing. I'd be great if I could upload more than one file for a bug report.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.14.14
ProcVersionSignature: Ubuntu 5.3.0-28.30~18.04.1-generic 5.3.13
Uname: Linux 5.3.0-28-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.9
Architecture: amd64
CasperVersion: 1.394.3
CurrentDesktop: KDE
Date: Tue Mar 31 01:16:54 2020
InstallCmdLine: file=/cdrom/preseed/kubuntu.seed boot=casper maybe-ubiquity initrd=/casper/initrd quiet splash --- maybe-ubiquity
LiveMediaBuild: Kubuntu 18.04.4 LTS "Bionic Beaver" - Release amd64 (20200203.1)
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)

[Ubuntu Foundations Team Bug Bot (crichton)]

Exception during installation:
Mar 30 23:07:17 kubuntu /plugininstall.py: Traceback (most recent call last):
Mar 30 23:07:17 kubuntu /plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 1725, in <module>
Mar 30 23:07:17 kubuntu /plugininstall.py: install.run()
Mar 30 23:07:17 kubuntu /plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 61, in wrapper
Mar 30 23:07:17 kubuntu /plugininstall.py: func(self)
Mar 30 23:07:17 kubuntu /plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 190, in run
Mar 30 23:07:17 kubuntu /plugininstall.py: self.configure_plugins()
Mar 30 23:07:17 kubuntu /plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 507, in configure_plugins
Mar 30 23:07:17 kubuntu /plugininstall.py: self.run_plugin(plugin)
Mar 30 23:07:17 kubuntu /plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 484, in run_plugin
Mar 30 23:07:17 kubuntu /plugininstall.py: "Plugin %s failed with code %s" % (plugin.NAME, ret))
Mar 30 23:07:17 kubuntu /plugininstall.py: ubiquity.install_misc.InstallStepError: Plugin usersetup failed with code 1
Mar 30 23:07:17 kubuntu /plugininstall.py: