Use absolute path for config.default.yaml in _helpers.py

[yerbol-akhmetov]

Changes proposed in this Pull Request

Good day. Here I propose to use absolute path to config.default.yaml in _helpers.py script. Such change is important while importing PyPSA-Earth rules elsewhere and running then in external directories within another Snakemake. This is helpful for setting workflow.

Checklist

• I consent to the release of this PR's code under the AGPLv3 license and non-code contributions under CC0-1.0 and CC-BY-4.0.
• I tested my contribution locally and it seems to work fine.
• A note for the release notes doc/release_notes.rst is amended in the format of previous release notes, including reference to the requested PR.

[yerbol-akhmetov]

We are still re-testing all rules execution with @GbotemiB. Unfortunately, these small changes were not sufficient for some rules, while it worked in one machine. We will let know when it is 100% ready.
@davide-f @ekatef

[yerbol-akhmetov]

With recent commit, prefix was identified for retrieve_databundle_light rule. Generally, a prefix is added to input and outputs of the imported rules automatically when prefix is defined as:

module pypsa_earth:
    snakefile:
        "submodules/pypsa-earth/Snakefile"
    config:
        config
    prefix:
        "submodules/pypsa-earth"

Those inputs and outputs (with prefix) are accessed properly when input and outputs of rules are defined explicitly as in almost all rules, except retrieve_databundle_light rule. Therefore, prefix is added inside of the retrieve_databundle_light.py script. It helps to match the inputs of following rule to outputs of preceding rule if Snakefile import is done. If snakemake is run in pypsa-earth directory (as regularly), then prefix is an empty string `` and rules are run regularly.

[davide-f]

Great @yerbol-akhmetov :D
This PR is ready to go functionality-wise! :D

Would you mind to fix the merge conflict? Than this is merged :)
Many thanks!

[yerbol-akhmetov]

Great @yerbol-akhmetov :D This PR is ready to go functionality-wise! :D

Would you mind to fix the merge conflict? Than this is merged :) Many thanks!

Thanks, @davide-f, for great help in testing and suggestions. I have resolved the conflicts and updated the branch.

[davide-f]

Thanks @yerbol-akhmetov :D