Catch specific errors from lftp retries/timeout

lftp has a max_retries set which allows the script to go on without hanging, I would like to handle the various errors (authentication failed, no host etc) better. Currently it logs the command from directly from lftp, but looks ugly:
`ls: Fatal error: max-retries exceeded (No route to host)`
`ls: Login failed: 530-Not logged in. WARNING: ACCESS BY UNAUTHORIZED PERSONS STRICTLY PROHIBITED.`