functions in cssutils/css/selector.py are too complex

[jaraco]

The code in selector.py is too complex, with lots of closures and entangled concerns.

 cssutils main @ pip-run mccabe -- -m mccabe cssutils/css/selector.py -m 10
202:4: 'Selector._setSelectorText' 88

[jaraco]

The module is much better now, with just three functions having complexity over 10:

 cssutils main @ pip-run mccabe -- -m mccabe cssutils/css/selector.py -m 10
66:4: 'New.append' 15
365:4: 'New._char' 13
765:4: 'Selector._prepare_tokens' 13

[jaraco]

I'm declaring this work good enough for now. It'd be nice to reduce the complexity more, but not enough to track in an issue.