Okay, I have kept track of the selector nesting level and if it reaches the end and is not back to zero, this is now detected as an error in my version of cssparser_v2.2.
Code:
KevinsiMac:cssparser2 kbhend$ ./release/cssparser/cssparser ~/Desktop/junk.css
Errors: 1
Error: 5: Unbalanced selector braces in style sheet
Warnings: 0
Information: 0
Pos: 0 Type: SEL_START Data: .kevin
Pos: 13 Type: PROPERTY Data: color
Pos: 20 Type: VALUE Data: blue
.kevin {
color:blue;