Raw string highlighting #337

Environment data

VS Code version: 1.18.1
Python Extension version: 0.80.0
Python Version: CPython 3.5.4 32b
OS and version: Windows 7 Pro SP1 x64

Actual behavior

I have the following line

fops.save_txt(environ['SystemRoot'] + r'\explorer.exe '
                      + bdexp.EXPORTS_DIR,
                      bpl.PROGS_TO_LAUNCH_PN)

and the r and \e shows in blue with the first ' and xplorer.exe ' shows in brown(?).
My point is that it isn't recognizing it as a string (raw in this case) like it does with the previous 'SystemRoot' which shows all brown(?) and the Intellisense recognizes as a string.

Expected behavior

It should show r'\explorer.exe ' all brown(?) and recognize it as a string.

Thanks,

JM