Subject: bug#39953: 27.0.50; [PATCH] explicitly fail if Emacs was configured with but cannot compile native JSON support

From: Noam Postavsky <[email-masked]>
Date: Mon, 09 Mar 2020 22:14:03 -0400

>> This patch explicitly fails ./configure if `--with-json' is passed but
>> cannot be fulfilled. Which means users without the Jansson headers
>> won't be able to compile Emacs unless explicitly disabling it with
>> `--without-json'; I don't know if that is too extreme,

This seems a bit too extreme to me, but I think giving an error on
missing Jansson headers only if --with-json is explicitly passed would
be okay.