py-soupsieve: updated to 1.8

1.8.0
NEW: Add custom selector support.
FIX: Small tweak to CSS identifier pattern to ensure it matches the CSS specification exactly. Specifically, you can't have an identifier of only -.
FIX: CSS string patterns should allow escaping newlines to span strings across multiple lines.
FIX: Newline regular expression for CSS newlines should treat \r\n as a single character, especially in cases such as string escapes: \\\r\n.
FIX: Allow -- as a valid identifier or identifier start.
FIX: Bad CSS syntax now raises a SelectorSyntaxError, which is still currently derived from SyntaxError, but will most likely be derived from Exception in the future.

(adam)