+
+ This all assumes the target system accepts ssh connections.
+ If it does not, the caller probably wants to stop trying
+ to reserve this system. Therefore this script can return 3 different codes.
+ Return code 0 means the reservation was successful.
+ Return code 1 means the system is inaccessible (or similarly unsuitable).
+ Return code 2 means the system is accessible, but already reserved.
+ The reason unsuitable systems return 1 is because that is also the value
+ Python returns on encountering and unexcepted exception.