#166 Replace format with f-strings

[roskakori]

• Close Replace .format() with f-strings #166.

[coveralls]

coverage: 96.255% (-0.004%) from 96.259%
when pulling 13c7af8 on 166-replace-format-with-f-strings
into 8fc754c on main.

[roskakori]

@ben05allen Thanks for your contribution, finally got to merge it.

I'm not sure when the next release will be, but this one will be included then.

I had to undo the included change for #152 because it was incomplete (also needs change in other parts), and I prefer to have it at a separate branch.