Ubuntu-18.04.2 nightly system update caused plymouth initramfs failure

[paranioid factoid]

After last night's system update, gdm3 can no longer start a display server. Looking into it, I found there was a failure building a new initramfs. Running kernel 4.18.0-25-lowlatency. Here's the error message. Have to type it in by hand as I'm using a pseudotty console on the affected machine.

# update-initramfs -u -v

[blah blah]

Calling hook plymouth
Adding binary /usr/lib/x86_64-linux-gnu/plymouth//script.so
E: /usr/share/initramfs-tools/hooks/plymouth failed with return 1
Removing /boot/initrd-img-4.18.0-25-lowlatency.dpkg-bak
update-initramfs: failed for /boot/initrd.img-4.18.0-25-lowlatency with 1
#

Please note the double slash between "plymouth//script.so" which is in the text of the error message.

I did attempt to reinstall plymouth.

# apt-get install --reinstall plymouth-*

which worked, in that it reinstalled, but did not succeed in rebuilding the kernel initramdisk.

[Steve Langasek (vorlon)]

Please run ubuntu-bug 1836717 if possible in order to collect additional information about your system state.

The most likely explanation for this is that you have a broken plymouth theme setting, which is causing the initramfs hook to be unable to correctly resolve the paths it needs in order to populate the initramfs, and it subsequently fails with an opaque error.

[Launchpad Janitor (janitor)]

[Expired for plymouth (Ubuntu) because there has been no activity for 60 days.]