[Lilypond-auto] [LilyIssues-auto] [testlilyissues:issues] Re: #5637 Port lilysong to subprocess module

In case we want to do this, I've submitted #5641 to remove both lilysong and lilymidi. Neither of them is mentioned in the documentation and I don't see any tests to make sure they actually work. I found `elisp/lilypond-song.el` to be related in that it call lilysong, so I'm proposing to remove

[Lilypond-auto] [LilyIssues-auto] [testlilyissues:issues] Re: #5637 Port lilysong to subprocess module

I haven't come across any and I'm absolutely fine with dropping it. Right now it's executed with `--help` during the build to generate the man page, so I wanted to fix it for Python 3. --- ** [issues:#5637] Port lilysong to subprocess module** **Status:** Started **Created:** Fri Dec 13,