cups-daemon upgrades stop cups-browsed and leave it stopped

[Marius Gedminas]

Whenever cups-daemon is upgraded (by unattended-upgrades usually), it stops cups-browsed as a side effect of the upgrade. While cups.service itself is restarted by the time the upgrade process is done, cups-browsed.service remains stopped until manual admin intervention, assuming the admin notices.

AFAIU this is because cups-browsed.service Requires=cups.service (among other things), so stopping cups.service during the preinst also stops cups-browsed.

I'm insufficiently proficient with systemd to suggest a fix.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: cups-daemon 2.1.3-4ubuntu0.6
ProcVersionSignature: Ubuntu 4.4.0-140.166-generic 4.4.162
Uname: Linux 4.4.0-140-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
Date: Tue Dec 11 13:33:13 2018
Lpstat: device for cream: dnssd://HP%20Color%20LaserJet%20MFP%20M477fdw%20(15A597)._ipp._tcp.local/?uuid=564e4238-4a35-484b-5944-a08cfd15a597
MachineType: System manufacturer System Product Name
Papersize: letter
PpdFiles: cream: HP Color LaserJet Pro MFP M477 Postscript (recommended)
ProcEnviron:
 LC_CTYPE=lt_LT.UTF-8
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-140-generic root=/dev/mapper/hostname-root ro nomdmonddf nomdmonisw
SourcePackage: cups
UpgradeStatus: Upgraded to xenial on 2016-11-07 (764 days ago)
dmi.bios.date: 08/14/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 2204
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: P8Z77-V LX
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: Rev X.0x
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr2204:bd08/14/2013:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKCOMPUTERINC.:rnP8Z77-VLX:rvrRevX.0x:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.name: System Product Name
dmi.product.version: System Version
dmi.sys.vendor: System manufacturer
modified.conffile..etc.default.cups:
 # Cups configure options

 # LOAD_LP_MODULE: enable/disable to load "lp" parallel printer driver module
 # LOAD_LP_MODULE has migrated to /etc/modules-load.d/cups-filters.conf
 # LOAD_LP_MODULE=yes
mtime.conffile..etc.default.cups: 2016-04-27T12:26:46