If you create a config file as utf-16 (easy to do unwittingly, e.g. with output
redirection in powershell) then gnupg programs will throw "invalid option".
I discovered this with gpg-agent when trying to add "enable-putty-support" to
gpg-agent.conf. If I edit the file (previously nonexistent) in notepad++, it is
saved by default as ASCII and there is no problem. If I create it using `echo
enable-putty-support > gpg-agent.conf`, then it gets created as utf-16 and is
utf-16 is the default encoding for many programs in Windows. gnupg on Windows
should either parse utf-16, or failing that throw an error clearly stating that
utf-16 config files are not supported.