Display command.longDescription in a preformatted block.
This makes the overall appearance of the page match what you would actually see from the console.
(Using: java -jar jenkins-cli.jar -s <URL> help <COMMAND>)
For some commands, such as SupportCommand (in support-core), this is critical,
since the expectation is that longDescription is a multiline fixed-width block.
Jenkins.getRootPath will never be null.
Misleading error message.
[FIXED JENKINS-25937] Treat BadPaddingException as an unloadable key and continue.