The prompt asking for media removal is neither shown at the end of the installation nor at 'normal' reboot nor poweroff

Bug report 'refresh':

This bug is affecting Lubuntu Xenial final, and I was adviced to create a new bug report. The symptoms are the same or similar as in

Bug #966480 The prompt asking for media removal is not shown at the end of the installation.

It affects the live session, when booted from a USB drive, when cloned (with mkusb, usb-creator-gtk, gnome-disks, dd, Win32 Disk Imager).

Workaround: remove the boot option 'splash', but if you know about it, you can press Enter to continue (rebooting or shutting down) with seeing the prompt.

This might also be a symptom of the same problem in the program code as reported in

Bug #1359689: cryptsetup password prompt not shown and/or
Bug #1370707: Plymouth does not display the graphical boot splash

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: plymouth 0.9.2-3ubuntu13
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic i686
ApportVersion: 2.20.1-0ubuntu2
Architecture: i386
CasperVersion: 1.375
CurrentDesktop: LXDE
Date: Wed Apr 20 04:10:55 2016
DefaultPlymouth: /usr/share/plymouth/themes/lubuntu-logo/lubuntu-logo.plymouth
LiveMediaBuild: Lubuntu 16.04 LTS "Xenial Xerus" - Release i386 (20160419)
MachineType: TOSHIBA SATELLITE PRO C850-19W
ProcCmdLine: file=/cdrom/preseed/username.seed boot=casper initrd=/casper/initrd.lz quiet splash --- debian-installer/language=sv keyboard-configuration/layoutcode?=se
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=sv_SE.UTF-8
 SHELL=/bin/bash
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: file=/cdrom/preseed/username.seed boot=casper initrd=/casper/initrd.lz quiet splash --- debian-installer/language=sv keyboard-configuration/layoutcode?=se
SourcePackage: plymouth
TextPlymouth: /usr/share/plymouth/themes/lubuntu-text/lubuntu-text.plymouth
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/24/2012
dmi.bios.vendor: Insyde Corp.
dmi.bios.version: 6.10
dmi.board.asset.tag: Type2 - Board Asset Tag
dmi.board.name: PLCSF8
dmi.board.vendor: Intel
dmi.board.version: Type2 - Board Version
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: OEM Chassis Manufacturer
dmi.chassis.version: OEM Chassis Version
dmi.modalias: dmi:bvnInsydeCorp.:bvr6.10:bd09/24/2012:svnTOSHIBA:pnSATELLITEPROC850-19W:pvrPSCBXE-00C00VN5:rvnIntel:rnPLCSF8:rvrType2-BoardVersion:cvnOEMChassisManufacturer:ct10:cvrOEMChassisVersion:
dmi.product.name: SATELLITE PRO C850-19W
dmi.product.version: PSCBXE-00C00VN5
dmi.sys.vendor: TOSHIBA