tests: add basic lxd test

[mvo5]

This adds a test to ensure that the basic lxd functionality is available. It covers that lxd as a snap is functional and that snaps inside an lxd container can be used.

[zyga]

NICE. Thank you for doing this! Just one nitipick

[zyga]

Do we need apt install -y here?

[mvo5]

Well, maybe, it is only needed if more dependencies pulled in but still a good idea, so +1

[fgimenez]

Supernice, thanks for this! Just a question about big downloads

[fgimenez]

Pardon my ignorance but, will this pull the container? If so and the download is big we could modify the images to include it from the beginning.

[mvo5]

Yes, it will download an image and the image is big(ish). So I'm happy about any suggestions that can improve the speed here :)

[fgimenez]

@mvo5 sorry for the very late response, IMO it's tricky because, given that we use lxd from the snap, if we initialize the linode image with it and put a container image in place, when the suite is initialized all the previous state would be whipped.

One possible solution could be to make the container image available at some well-known location in the linode image and, after the lxd snap is installed during the test, move the container image files to /var/snap/lxd/common/lxd/images, so that we don't need to download it during the test, do you think that would be a good approach?

[sergiocazzolato]

Should you need to run on restore stop and delete for the container?

[pedronis]

@mvo5 what's the state of this? it seems lxd doesn't work in the autopkgtests, the spread ones seems unrelated but not sure

[codecov-io]

Codecov Report

Merging #3372 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3372      +/-   ##
==========================================
+ Coverage   75.63%   75.64%   +<.01%     
==========================================
  Files         407      407              
  Lines       35034    35034              
==========================================
+ Hits        26499    26502       +3     
+ Misses       6654     6652       -2     
+ Partials     1881     1880       -1

Impacted Files	Coverage Δ
interfaces/sorting.go	98.71% <0%> (-1.29%)	⬇️
cmd/snap/cmd_aliases.go	95% <0%> (+1.66%)	⬆️
wrappers/binaries.go	79.54% <0%> (+6.81%)	⬆️

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[zyga]

+1, some comments to fix perhaps

[zyga]

You need to tweak this to exclude fedora and openSUSE though ideally only after checking it really doesn't work there

[chipaca]

The test failures (in travis and xenial-i386 at least) are germane.
What's the status of this PR?

[sergiocazzolato]

This is a huge download if I need to run the whole suite locally on qemu, it will take hours, perhaps this kind of tests could be just executed on linode or nightly.

[mvo5]

Closing for now until I find time to actually make the test work everywhere.

[mvo5]

Reopening to get another full spread run after tweaking the test slightly. It should indeed go to the night suite as @sergiocazzolato suggested.

[mvo5]

This should work now #3815 is merged and we can install snaps that have bash completion files on core again.

[niemeyer]

LGTM, but it's worth noticing that the new tests takes 2 to 3 minutes to run. We're back at 30+ minutes.