variables.css defined in localgov_elections.libraries.yml does not exist

[ctorgalson]

Description

The module libraries file specifies a file named variables.css in several places, but the module contains no such file:

A quick look shows few css variables in use, some of them having names used in localgov_base, but there are others that are presumably missing.

[markconroy]

1. Let's definitely remove references to variables.css if it doesn't exist.
2. It's a while since I worked on this module, but I have a feeling those other variables --green-party etc are set in the module/CMS somewhere and used as backgrounds depending on who wins an election. EDIT: Maybe I'm just thinking of when we set up default parties here: https://github.com/localgovdrupal/localgov_elections/blob/1.x/modules/localgov_elections_uk_parties/localgov_elections_uk_parties.install

We should probably update them to something like --lgd-election-green-party, --lgd-election-conservatives, etc.

@chriswales95 Could you weigh in on this one if you have a moment?