Fixed unhandled exception when VM allocation fails

                    except Exception as err:

                        results_by_vm[vmspec['title']] = 'Error: %s' % err

                        errors += 1

                        continue

                    else:

                        self.logger.info('VM %s: spawned on %s' % (vmspec['title'], target_hv_name))

                        results_by_vm[vmspec['title']] = 'spawned %s on %s' % (vm_uuid, target_hv_name)