Just for the record, I think you read this a bit too fast before
closing:

Terry J. Reedy writes:
> I am closing this as some combination of wrong, inapplicable,
> out-of-date, and postponed.
> 
> 1. (...) For bz2, there is "This module provides a
> comprehensive interface for the bz2 compression library." If the library
> is not there, then the module obviously cannot function.

The point of the request was to move that error from runtime to compile
time.  As a configuration option, not by default, since as you say:

> 2. I think the current default build process is right for most users.

Indeed.

> 4. This seems to have become pretty much a non-issue. The OP says he has
> no further concrete interest because "It's been a while since I had a
> computer without these libraries...". I am suspecting this is pretty
> much true for everyone who might otherwise care enough to provide a
> patch.

Half right - actually I _would_ still prefer that bit of safety, but
OTOH I probably won't be providing a patch anytime soon.  (Still, I can
always reopen the issue if I do write one.)