Improve reporting of 'Unable to verify asset'

[steilerDev]

  Hello,

Despite the max-retries at -1 by default, the sync cuts out on various errors such as the one below after less than 10/20 minutes.

• If I pass the cron to "* * * * *" do I have a chance of having the script running continuously?
• Is the lock released after a fatal error?
• If I run the script with the --force param every minute and the script actually runs without crashing, what happens?

Thanks !

Originally posted by @Laffreux-dev in #154

[steilerDev]

Closed with f66ad1a