pre_backup_retry_script
:   Hook script launched before a base backup, after 'pre_backup_script'.
    Being this a _retry_ hook script, Barman will retry the execution of the
    script until this either returns a SUCCESS (0), an ABORT_CONTINUE (62) or
    an ABORT_STOP (63) code. Returning ABORT_STOP will propagate the failure at
    a higher level and interrupt the backup operation.

    Scope: Global/Server.
