Crikey ApcuCache.php: failed to open stream: No such file or directory

Here’s the full error message:
include(/var/roger-parkinson-site/www/html/vendor/composer/…/doctrine/cache/lib/Doctrine/Common/Cache/ApcuCache.php): failed to open stream: No such file or directory

What I’m doing is migrating this (working) site to a new machine. So I copied all the files over… not the caches though.I don’t need to copy the caches, right? But this missing file is supposed to be in a cache. I looked at the working site and it is missing from there, although that doesn’t cause a problem.

Now I’m not just copying, I’m moving from php 7.1 to 7.2, I also had to mess about with permissions on the new machine, mostly 'cos I did them badly last time. But none of those seem relevant. Does anyone know why it needs this file and where it should get it from?

I got past this by copying the cache dir over. Still puzzled how it got there the first time but it works now.