Updating PHP broke roundcube again; how I fixed it again

A while after I upgraded my server to CentOS 7, WordPress started griping about needing newer PHP in order to install the latest PHP. I knew this caused problems with roundcube in my CentOS installation, so I was ready for it to happen again. 

Good thing, too.  To update PHP, I installed the remi repos for EL7 and decided to go with the latest, PHP 7.3.  WordPress updated just fine afterwards, and I was ready to test roundcube.

Borked.  Again.

Try to login, and you get “Invalid request”. The log file showed “Parameter must be an array or an object that implements Countable” related to my choice of time zone.  Searching that up, I saw I wasn’t the only one with the issue, and that newer versions of roundcube should clear this up.

But I use CentOS, which comes straight from RHEL, which favors keeping slightly older, more stable versions of packages over bleeding edge (“if you want bleeding edge”, they say, “download Rawhide!”). Fortunately for me, the fix was simple: remi keeps a version of roundcubemail right there in the repo.  Not the safe repo, but the (supposedly not-quite-as-safe) “regular” repo.  I enabled that, and did a yum update roundcubemail.

Problem solved.