Description
When I run some commands that make use of the cache, I get this:

$ ./bin/console app:some-command

10:45:08 WARNING [cache] Failed to save key "... some key ..." (array)
["key" => "... some key ...", "type" => "array", "exception" => null]
["log_uuid" => "cf01082a-0f5f-4b36-86e9-3b5a5ee6832a"]

No additional info is provided on dev.log either, so this is tricky to debug. Thanks to @nicolas-grekas this was restricted to either a serialization problem of the cached content or the use of APCu-based cache. In this case it wasn't a serialization issue because the content was a simple array.

Let's check if we can add more error messages (or improve the existing ones) to explain the error in more detail and provide, if possible, solutions to fix them. Thanks!