skpkg: apply black line-length 115 to all files in the project directory

[dabeycorn]

No description provided.

[dabeycorn]

@sbillinge ready for review. I left the line length at 115 because that was what it was set to. Should I change the value to 79 to stay under 80?

[sbillinge]

wow, great job! Let's leave the line-length at 115 for now, but I would ideally like to change it back to 79 to standardize things. This will generate a bunch of manual work though and we may decide it is not the top priority to do it here. We can make a new branch later when we have all the pre-commit installed and working an run flake8 to see how much work it will be. For now, tihs is good.

I have created a migration branch, so will merge this into migration. Please use that as the base branch for all this skpkg work. I.e., new branches will be created so:

git checkout migration
git pull upstream migration
git checkout -b newbranch

and when you make the PR, select the migration branch on the diffpy repo as the base branch