package python-gi 3.12.0-1ubuntu1 failed to install/upgrade: subprocess new pre-removal script returned error exit status 137

[Nevil Brownlere]

I'm running Ubuntu 114.04 on a 32-bit Lenovo T61.
When I try to launch alacarte from the menus or from the command line I get
$ alacarte
Traceback (most recent call last):
  File "/usr/bin/alacarte", line 23, in <module>
    from Alacarte.MainWindow import main
  File "/usr/share/alacarte/Alacarte/MainWindow.py", line 20, in <module>
    import gi
  File "/usr/lib/python3/dist-packages/gi/__init__.py", line 36, in <module>
    from ._gi import _gobject
ModuleNotFoundError: No module named 'gi._gi'

Web pages I've looked at suggest reinstalling python3-gi, but apt-get and
Synaptic won't do that for me - instead apt-get locks up in a tight 100% processor usage loop.

ProblemType: Package
DistroRelease: Ubuntu 14.04
Package: python-gi 3.12.0-1ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-148.174~14.04.1-generic 4.4.177
Uname: Linux 4.4.0-148-generic i686
NonfreeKernelModules: nvidia
ApportVersion: 2.14.1-0ubuntu3.29
AptOrdering:
 python-gi: Install
 python3-gi: Install
 python-gi: Configure
 python3-gi: Configure
Architecture: i386
Date: Fri Jul 19 16:08:12 2019
DuplicateSignature: package:python-gi:3.12.0-1ubuntu1:subprocess new pre-removal script returned error exit status 137
ErrorMessage: subprocess new pre-removal script returned error exit status 137
InstallationDate: Installed on 2016-05-13 (1162 days ago)
InstallationMedia: Ubuntu 14.04.4 LTS "Trusty Tahr" - Release i386 (20160217.1)
RelatedPackageVersions:
 dpkg 1.17.5ubuntu5.8
 apt 1.0.1ubuntu2.23
SourcePackage: pygobject
Title: package python-gi 3.12.0-1ubuntu1 failed to install/upgrade: subprocess new pre-removal script returned error exit status 137
UpgradeStatus: No upgrade log present (probably fresh install)