Removes a system by id.
        Usage: sftpman rm {system_id}..
        For a list of system ids, see `sftpman ls available`.

def command_rm(self, system_id, *system_ids):
        """Removes a system by id.
        Usage: sftpman rm {system_id}..
        For a list of system ids, see `sftpman ls available`.
        """
        # Intentionally reading the first system_id separately,
        # because it's required. The others are optional.
        # This ensures that we'll generate an error if someone tries to call
        # this without the required argument.
        system_ids = (system_id,) + system_ids
        has_failed = False
        for system_id in system_ids:
            try:
                system = SystemModel.create_by_id(system_id, self.environment)
                controller = SystemControllerModel(system, self.environment)
                controller.unmount()
                system.delete(self.environment)
            except SftpException as e:
                sys.stderr.write('Cannot remove %s: %s\n' % (system_id, str(e)))
                has_failed = True
        if has_failed:
            sys.exit(1)