On many (all?) Jenkins startups, I was seeing the following WARN:

Mar 27, 2018 10:04:00 PM Main deleteWinstoneTempContents
WARNING: Failed to delete the temporary Winstone file /tmp/winstone/jenkins-2.112.war

After a quick look at the code, it seems like this is just because /tmp/winstone/jenkins-2.112.war can be absent.
I think we can modify the code to just not log anything if the file to remove is not found.