Fix a bug "WinError 6"

https://github.com/SublimeText/CTags/issues/192

I use Windows 7 x64.

When I run command "Rebuild Tags" http://i.imgur.com/rA6VoPp.png , and choose "All Open Folders" http://i.imgur.com/WtT5ejb.png , I get error - "WinError 6" http://i.imgur.com/g1xVFHQ.png

This commit fix this problem for me.