Integration test regression on LXD 4.0

[simondeziel]

#584 introduced support for custom volume snapshot management and added additional tests. One of the additional tests now fails on LXD 4.0:

================================================================ FAILURES ================================================================
________________________________ TestStorageVolumeSnapshot.test_create_get_restore_delete_volume_snapshot ________________________________

self = <integration.test_storage.TestStorageVolumeSnapshot testMethod=test_create_get_restore_delete_volume_snapshot>

    def test_create_get_restore_delete_volume_snapshot(self):
        # Create pool and volume
        pool = self.create_storage_pool()
        self.addCleanup(self.delete_storage_pool, pool)
    
        volume = self.create_storage_volume(pool, "vol1")
        self.addCleanup(self.delete_storage_volume, pool, "vol1")
    
        # Create a few snapshots
>       first_snapshot = volume.snapshots.create()

integration/test_storage.py:153: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

cls = <class 'pylxd.models.storage_pool.StorageVolumeSnapshot'>
volume = <pylxd.models.storage_pool.StorageVolume object at 0x786d535bad30>, name = None, expires_at = None

    @classmethod
    def create(cls, volume, name=None, expires_at=None):
        """Create new :class:`pylxd.models.StorageVolumeSnapshot` object from the current volume state using the given attributes.
    
        Implements POST /1.0/storage-pools/<pool>/volumes/custom/<volume_name>/snapshots
    
        :param volume: :class:`pylxd.models.StorageVolume` object that represents the target volume to take the snapshot from
        :type volume: :class:`pylxd.models.StorageVolume`
        :param name: Optional parameter. Name of the created snapshot. The snapshot will be called "snap{index}" by default.
        :type name: str
        :param expires_at: Optional parameter. Expiration time for the created snapshot in ISO 8601 format. No expiration date by default.
        :type name: str
        :returns: a storage volume snapshot if successful, raises an exception otherwise.
        :rtype: :class:`pylxd.models.StorageVolume`
        :raises: :class:`pylxd.exceptions.LXDAPIExtensionNotAvailable` if the
            'storage_api_volume_snapshots' api extension is missing.
        :raises: :class:`pylxd.exceptions.LXDAPIException` if the the operation fails.
        """
        volume.client.assert_has_api_extension("storage_api_volume_snapshots")
    
        response = volume.api.snapshots.post(
            json={"name": name, "expires_at": expires_at}
        )
    
        operation = volume.client.operations.wait_for_operation(
            response.json()["operation"]
        )
    
        # Extract the snapshot name from the response JSON in case it was not provided
        if not name:
>           name = operation.resources["storage_volume_snapshots"][0].split("/")[-1]
E           KeyError: 'storage_volume_snapshots'

pylxd/models/storage_pool.py:783: KeyError

An easy way to reproduce this is with ./integration/run-integration-tests-in-lxd focal.

The issue seems to be that LXD 4.0's operation data looks like this:

{'storage_volumes': ['/1.0/storage_volumes/vol1']}

While with a newer LXD, it looks like this:

{'storage_volume_snapshots': ['/1.0/storage-pools/tyg1/volumes/custom/vol1/snapshots/snap0'], 'storage_volumes': ['/1.0/storage-pools/tyg1/volumes/custom/vol1']}

Unfortunately, I couldn't trace any specific API extension related to the addition of the storage_volume_snapshots key.