File engine should not use drupal_set_message?

There are some rare cases where a cache file cannot be created. I think that in these case the user should not be informed with the drupal_set_message() because there's nothing he can do about that (I don't know if the watchdog is available then).

Btw, this is one file that could not be created:

/home/httpd/hydra.radioradicale.it/sites/fainotizia/cache/cache/3/3e0fe73b52a72faf9ab3f48d120cb84f--localemap:it:http:--www.fainotizia.it-sites-fainotizia2-themes-radioradicale-FlowPlay...