I am really sorry for disturbing,but I have tested several vision of rhino in windows 7 including rhino 6.12/6.2/6.5/6.8.
Same mistake shows in the exact same line of runmanager_bluecfd.py and case.py listed above.
when it comes to rhino 6.12/6.2 which means that there’s no need to install microsoftvisualc++2017, the error goes"Unable to translate bytes [BE] at index 0 from specified code page to Unicode" which happened in a HB issue here.
When it comes to 6.5/6.8, the error is as same as the problems listed above. I am poor in Python but may be these messages can be of little help.