package backport-iwlwifi-dkms 8324-0ubuntu1 failed to install/upgrade: installed backport-iwlwifi-dkms package post-installation script subprocess returned error exit status 10

[SRU Justification]

[Impact]

backport-iwlwifi-dkms of latest upstream revision 8324 has no updates for a few months and is becoming a problem when installed against recent kernels >= v5.4. It's reported to have poor network throughput for 7000/8000/9000 series cards.

[Fix]

On Bionic and Eoan, we've skipped module install against kernel >= v5.0 because we have backported drivers for new device models as much as we can. On Focal and on, the in-tree kernel iwlwifi driver is currently much more up to date in comparison to backport-iwlwifi-dkms, so there should be no more reason to install it automatically via modaliases.

So two actions to be taken here:
* to remove modaliases for the dkms package, so that it won't be installed automatically via "3rd party drivers".
* to mark OBSOLETED_BY kernel 5.4.0 and up

[Test Case]

* For new installations, this means backport-iwlwifi-dkms shouldn't be installed automatically even with a PCI id match.
* For existing installations, dkms modules will still be built, but the module installation will be skipped, leaving messages like:

  $ dkms status
  backport-iwlwifi, 8324, 5.4.0-33-generic, x86_64: installed
  (WARNING! Diff between built and installed module!) (WARNING!
  Diff between built and installed module!) (WARNING! Diff
  between built and installed module!) (WARNING! Diff between
  built and installed module!) (WARNING! Diff between built and
  installed module!) (WARNING! Diff between built and installed
  module!)

This can also be tested locally with follow command against packages prebuilt in https://launchpad.net/~vicamo/+archive/ubuntu/ppa-1863583:

  sudo env AUTOPKGTEST_ARTIFACTS=/tmp debian/tests/dkms-autopkgtest

[Regression Potential]
Low. Moving to in-tree drivers instead.

[Other Info]
Focal SRU package for landing in https://launchpad.net/~vicamo/+archive/ubuntu/ppa-1863583 .

========== Original Bug Description ==========

no wifi detected
and when upgrade it's aborted and return error code
system used ubuntu 20.04
kernel 5.4
laptop dell xps 15 7590

ProblemType: Package
DistroRelease: Ubuntu 20.04
Package: backport-iwlwifi-dkms 8324-0ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-12.15-generic 5.4.8
Uname: Linux 5.4.0-12-generic x86_64
ApportVersion: 2.20.11-0ubuntu16
Architecture: amd64
Date: Mon Feb 17 10:22:57 2020
ErrorMessage: installed backport-iwlwifi-dkms package post-installation script subprocess returned error exit status 10
InstallationDate: Installed on 2020-02-05 (12 days ago)
InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
PackageArchitecture: all
Python3Details: /usr/bin/python3.7, Python 3.7.6, python3-minimal, 3.7.5-1ubuntu1
PythonDetails: N/A
RelatedPackageVersions:
 dpkg 1.19.7ubuntu2
 apt 1.9.9
SourcePackage: backport-iwlwifi-dkms
Title: package backport-iwlwifi-dkms 8324-0ubuntu1 failed to install/upgrade: installed backport-iwlwifi-dkms package post-installation script subprocess returned error exit status 10
UpgradeStatus: Upgraded to focal on 2020-02-07 (9 days ago)