BUG: Ubuntu package doesn't return proper error code on failure

[Florian Anderiasch]

Hi,
please excuse if this is the wrong medium to report this error, but I
couldn't manage to file a bug on Launchpad.

Ubuntu 18.04
4.15.0-45-generic
wireguard-dkms                                  0.0.20190123-wg1~bionic

wireguard-dkms failed to install properly because the kernel module
could not be compiled (my bad, has nothing to do with this bug report),
but the installation exited with exit code 0 and so I didn't realize at
first because everything scrolled past. IMHO this should be a non-zero
exit code because wireguard was obviously not working because I couldn't
modprobe the kernel module.

apt-get install --reinstall wireguard-dkms
  Reading package lists... Done
  Building dependency tree
  Reading state information... Done
  0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 0 not
upgraded.
  Need to get 551 kB of archives.
  After this operation, 0 B of additional disk space will be used.
  Get:1 http://ppa.launchpad.net/wireguard/wireguard/ubuntu bionic/main
amd64 wireguard-dkms all 0.0.20190123-wg1~bionic [551 kB]
  Fetched 551 kB in 0s (1.589 kB/s)
  (Reading database ... 278642 files and directories currently installed.)
  Preparing to unpack .../wireguard-dkms_0.0.20190123-wg1~bionic_all.deb ...

  ------------------------------
  Deleting module version: 0.0.20190123
  completely from the DKMS tree.
  ------------------------------
  Done.
  Unpacking wireguard-dkms (0.0.20190123-wg1~bionic) over
(0.0.20190123-wg1~bionic) ...
  Setting up wireguard-dkms (0.0.20190123-wg1~bionic) ...
  Loading new wireguard-0.0.20190123 DKMS files...
  Building for 4.15.0-45-generic
  Building initial module for 4.15.0-45-generic
  Error! Bad return status for module build on kernel: 4.15.0-45-generic
(x86_64)
  Consult /var/lib/dkms/wireguard/0.0.20190123/build/make.log for more
information.

The real cause of the error was me using the LLVM linker lld as
/usr/bin/lld - which unsurprisingly doesn't build kernel modules, not
that it matters for this.

Everything is working now flawlessly, thanks for your efforts :)

Cheers,
Florian