fetch: does not fail when the remote file does not exist

Does this make sense?
If I try to fetch a file that does not exist, it returns status "ok". When I run it with -vvv, I see:

"msg": "the remote file does not exist, not transferring, ignored"

Shouldn't it fail?

If I recall correctly, it's actually a feature, because a particular
logfile may not be present on a remote host, etc.

Could we add an option to have it either way?
I can see not failing when it's a log file, but needing it to fail when it is an important file which will be used by the next task.

Sure.

I can see a fail_on_missing=True being an option.

We should definitely document the current behavior. It was original
done as a very lightweight backup system.

Precede the fetch with

file: path=/path/to/file/to/be/fetched state=file