Poetry2nixify nixops_gcp + Python3 migration

[tewfik-ghariani]

After fixing the broken bootstrap resource per https://github.com/AmineChikhaoui/nixops-gce/pull/1 and making the plugin work again, I wanted to work on upgrading the python version used as the main nixops is already using python3

And then I stumbled upon the new initiative to move to Poetry as dependency manager so here I am, bringing nixops_gcp up to speed :smiley:

This PR includes :

• Use Poetry & Poetry2nix for environment and plugin management https://github.com/NixOS/nixops/pull/1256
• Migrate to python 3 : https://github.com/AmineChikhaoui/nixops-gce/issues/2
• Renaming the main folder to nixops_gcp
• Updating README and adding .gitignore
• Blackify the python scripts

Followed the authoring guidelines shared per: https://github.com/NixOS/nixops/blob/master/doc/plugins/authoring.rst

Tested all sort of actions and everything seems to be working fine. The only problem I faced in the "check" operation as it fails saying that it cannot operate on a 'closed database'

Not sure if this is a 'dev-shell' limitation or if I'm missing something

EDIT The check operation has been fixed per https://github.com/NixOS/nixops/pull/1334

Thanks @adisbladis for leading the initiative and @grahamc for your hard work

cc @AmineChikhaoui can you review and merge this please :)

[AmineChikhaoui]

@tewfik-ghariani Great :tada: , thanks.

Quick comments:

• can you split the blackify commit into its own PR, changes over the whole repo makes it hard to review the other changes in the PR.
• I don't see mypy type annotations, were you able to convert to python3 without the help of mypy ?

[tewfik-ghariani]

@AmineChikhaoui adding mypy type annotations seems to be a manual and lengthy process. Can we review and merge this PR and after that include mypy? That way even others may contribute and help cover all functions/variables and it least we would have the nixops-gce plugin working using poetry