What an annoying and useless error. Here’s how to fix it, but there isn’t much to it.
You get the error when running this command.
$ pecl upgrade
pear.php.net is using a unsupported protocol - This should never happen.
upgrade failed
The fix? First upgrade the pear channels, then the pecl channels.
$ pear update-channels
$ pecl update-channels
Next, do a pear and pecl upgrade.
$ pear upgrade
...
(may update a lot of pear packages)
$ pecl upgrade
Nothing to upgrade
It’s not clear to me why this is even an issue in the first place, but it apparently is.