There was some big upgrade - from the recently installed Ubuntu Mate 15.10 to 16.04 - which took a fair long time, however, it ended with some error, which the above was part of. Then I ran Synaptic, which had 2 broken packages, so after those were fixed, there were still some outstanding updates marked and I ran those...
ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: menu 2.1.47ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
Date: Fri Apr 22 12:43:17 2016
Dependencies:
gcc-5-base 5.3.1-14ubuntu2
gcc-6-base 6.0.1-0ubuntu1
libc6 2.23-0ubuntu3
libgcc1 1:6.0.1-0ubuntu1
libstdc++6 5.3.1-14ubuntu2
ErrorMessage: dependency problems - leaving triggers unprocessed
InstallationDate: Installed on 2016-01-31 (81 days ago)
InstallationMedia: Ubuntu-MATE 15.10 "Wily Werewolf" - Release amd64 (20151021)
RelatedPackageVersions:
dpkg 1.18.4ubuntu1
apt 1.2.10ubuntu1
SourcePackage: menu
Title: package menu 2.1.47ubuntu1 failed to install/upgrade: dependency problems - leaving triggers unprocessed
UpgradeStatus: Upgraded to xenial on 2016-04-22 (0 days ago)
Status changed to 'Confirmed' because the bug affects multiple users.