I have Sublime Text 2 build 2165. It seems the Python syntax highlighter doesn't support raw text strings with open square brackets. Consider this Python code:
val = (r'', ''),
I enter this code into a blank Python file, and the syntax highlighter considers everything after "r'" to be part of the string, and the remainder of the file is colored purple.
I have one plugin installed (sublimelinter). I don't think the linter would break the syntax highlighting, but please let me know if I should test without it.