ubuntu-mate qa-test install focal.2 : ubi-partman failed with exit code 10.

Ubuntu-MATE QA-test install on
-
hp dc7700 (c2d-e6320, 5gb, nvidia quadro nvs 290)
as requested (to explore a different bug report)

I selected the wrong option, so used to BACK to step back in ubiquity.. then this occurred.

I exited ubiquity, then re-started it and the error was appearing now each time.

As my purpose was looking for a specific test, I re-start box (REISUB) & issue did not re-occur (no BACK buttons pressed next time being more careful).

I've noted a few recent support queries about this error in recent ~week.

This is likely duplicate (there are many like it, eg. https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1836782), mostly filing this bug as don't have time to deal with it currently.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.15.10
ProcVersionSignature: Ubuntu 5.8.0-43.49~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-43-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.445.1
CurrentDesktop: MATE
Date: Thu Feb 11 23:36:45 2021
InstallCmdLine: file=/cdrom/preseed/ubuntu-mate.seed initrd=/casper/initrd quiet splash ---
LiveMediaBuild: Ubuntu-MATE 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)