Dont use shellwords with windows

> Shellwords

> Manipulates strings like the UNIX Bourne shell¶ ↑

> This module manipulates strings according to the word parsing rules of the UNIX Bourne shell.

> The shellwords() function was originally a port of shellwords.pl, but modified to conform to POSIX / SUSv3 (IEEE Std 1003.1-2001 [1]).

Shellwords obeys posix rules, these don't seem to work on Windows, (#1713) so we should do something differently on Windows.
I backported this as although it's a new feature, it's only used internally.