Force series16 to install dependencies

[Hook25]

Description

Right now the series16 snap does not install the dependencies. The reason seems to be that the latest version that support python3.5 does not support reading dependencies from pyproject.

This forces the install of dependencies in the snapcraft.yaml.

Also, in order to detect any funny business in the future with dependencies, this adds a very simple test and metabox scenario that tries to import every dependency.

Resolved issues

Checkbox16 2.9.1 is broken
Metabox coverage of dependencies was lacking

Documentation

This also documents why every step of the install is done in more detail with comments

Tests

This adds a new metabox test. To run it call metabox with the VerifyInstallation tag like this:

metabox --tag VerifyInstallation local-source-16.04.py

To test a custom built snap create a metabox configuration (snap-16.04.py):

configuration = {
    "local": {
        "origin": "classic-snap",
        "checkbox_snap": {"uri": "~/checkbox16.snap"},
        "checkbox_core_snap": {"risk": "edge"},
        "releases": ["xenial"],
    },
}

Build the checkbox16 snap and put it in the location you specified above, then run:

metabox --tag VerifyInstallation snap-16.04.py

[kissiel]

The whole premise is great! I absolutely love it and we NEED this. Having said that this IMHO requires some rework.
All the deps in this test should be handled the same way as there are when building checkbox, so we actually test the thing. This also (heavily) applies to transitive dependencies. And the version locks.

I think embedding this test in a test plan is unnecessary. This can be just a job and I'd use checkbox-cli -run
I also think those import from within a job run by Checkbox is not the way the modules would be used. The jobs don't import Checkbox's logic. They do import checkbox-support's logic.

To test if Checkbox can import modules it should have this need to be tested in the same environment that checkbox would run. We facilitated debugging of similar issues in the past by providing the shell entry point to the snap. It has (or at least should have :) ) the same environment as checkbox-cli would have.

Lastly, does the provided example metabox --tag VerifyInstallation local-source-16.04.py even work? VerifyInstallaiton is not a tag. Is the scenario class name automatically appended to the list of tags the scenario has?

[pieqq]

Maciek already covered a lot. I'm just the annoying typo guy here. :D

[kissiel]

Great stuff!
Thanks for all the improvements!

[pieqq]

I understand that you had a long discussion with Maciek, so we should be all good now. Thanks!

[pieqq]

(we have to fix those chain scenarios...)