[pkg-go] Bug#989145: Please do not use uml fakemachine backend in the DEP-8 test

[Steve Langasek]

The options for fakemachine backend are uml and kvm.  Having this test use
KVM is not any more help for Ubuntu, because our test runners are all VMs
and nested KVM is not a supported configuration.

So switching the test to use KVM instead of UML is of no further value to
Ubuntu.

I'm not sure that the debos package works at all on Ubuntu; attempting to
manually run the autopkgtest with the KVM backend instead of the UML backend
gives me incomprehensible results:

$ sudo sh -x debian/tests/build-chroot 
+ : /tmp/debos-1.0.0+git20201203.e939090/debian/tests
+ debos /tmp/debos-1.0.0+git20201203.e939090/debian/tests/example.yaml
open /tmp/fakemachine-959458465/result: no such file or directory
$

Running debos with --show-boot gives me:

[...]
modprobe: can't load module netfs (kernel/fs/netfs/netfs.ko): No such file or directory
mount: mounting usr on /usr failed: No such device
mount: mounting sbin on /sbin failed: No such device
mount: mounting bin on /bin failed: No such device
mount: mounting lib on /lib failed: No such device
/init: exec: line 2[8:  / li b/ sy1.202353] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00007f00
[    1.203274] CPU: 0 PID: 1 Comm: init Not tainted 5.13.0-17-generic #17-Ubuntu
s[te md /s ys te1md.: 2n04120] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
[    1.205101] Call Trace:
ot f[ou nd 
  1.205402]  show_stack+0x52/0x58
[    1.205875]  dump_stack+0x7d/0x9c
[    1.206300]  panic+0x101/0x2e3
[...]

(the netfs.ko module does exist in the host environment at
/lib/modules/5.13.0-17-generic/kernel/fs/netfs/netfs.ko, so I don't know why
this fails.)

So from what I can see, the package:
- cannot have meaningful autopkgtests on Ubuntu
- currently does not work on Ubuntu unless passing --disable-fakemachine,
  and then only as root

We could switch the autopkgtest to use --disable-fakemachine in Ubuntu
(this wouldn't be an appropriate change to make in Debian).  Is it better to
do this, or to drop the package from Ubuntu?  If it doesn't work in the
default configuration, does it make sense to have this package in Ubuntu?

My current suggestion is:
- ask for an additional autopkgtest in Debian that runs with debos
  --disable-fakemachine (instead of replacing the current autopkgtest)
- introduce an Ubuntu delta that drops the autopkgtest which depends on
  fakemachine
- optionally, patch debos in Ubuntu to use --disable-fakemachine by default?

Lukas, what do you think?

Andrej, Héctor, do you think it makes sanse to add an additional
--disable-fakemachine autopkgtest to debos?  (If not, this bug can just be
closed, and we should handle it all on the Ubuntu side.)

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                   https://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org
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