Flag Not setting a value in cache when a failure happens

As in people only cache on success.

Start by locating the cache behavior related to failures in this PHP_CodeSniffer ruleset, then trace when values are written after a failed operation. Clarify whether failures should be cached, identify the relevant existing tests if any, and verify the intended behavior with a regression test; the issue provides no file or test location.

Written by the indexing model from the issue text.