'Check if it is possible to execute live migration.
This checks if the live migration can succeed, based on the
results from check_can_live_migrate_destination.
:param context: security context
:param instance: nova.db.sqlalchemy.models.Instance
:param dest_check_data: result of check_can_live_migrate_destination
:param block_device_info: result of _get_instance_block_device_info
:returns: a LiveMigrateData object'

def check_can_live_migrate_source(self, context, instance, dest_check_data, block_device_info=None):

    raise NotImplementedError()
