Mike Latimer authored Jan 26, 2015 and Daniel P. Berrangé committed Jan 27, 2015

When TCK cleans up a test domain, existing snapshots are deleted. However,
not all drivers (e.g. libxl) support snapshots. When such a driver is
involved, the following error is reported and the testkit fails to cleanup
the domain:

  libvirt error code: 3, message: this function is not supported by the
  connection driver: virDomainSnapshotNum

Rather than erroring out, list_snapshots should be protected using eval. In
the event the underlying driver does not support snapshots, an empty list is
returned, and no snapshot deletion is attempted. (Note - It is the listing
of snapshots that is causing the error, not the attempt to delete them.)