This renders _get_build_version unused. Can it be removed?

@ZeroIntensity, as you'll be doing this more often: consider doing deprecation periods for underscored API as well, if there's no harm in keeping things around for a few more years.
Most of the module predates clear docs on what the underscore means, so existing code might use such functions.

Ah, right, thanks for the reminder. I think this one is okay because I couldn't find any uses of it after a quick code search.

Yeah, this is more of a general reminder of what to keep in mind.
As for code searches, be careful -- this stuff also predates GitHub's hegemony.