I think this is worse because once you have a python 3 only syntax in your script (such as f-string), python 2 will simply throw syntax error because it need to

I think this is worse because once you have a python 3 only syntax in your script (such as f-string), python 2 will simply throw syntax error because it need to parse the file to execute. The original solution looks hacky, but it can actually inform user to use python 3.