Lxc-destroy fails: has clones

On debian stretch with lxc version 2, I cannot destroy a container: answer is “Destroying ccc failed: ccc has clones”.
lxc-destroy -n ccc -s has same result. What can I do to force destruction?
I didn’t find a way to list clones depending on this container.
The container was probably created long ago (in jessie with lxc v 1).

I think there should be a file in /var/lib/lxc/ccc that lists those clones.

$ ls -1sh /var/lib/lxc/ccc
total 12K
4,0K config
0 fstab
4,0K lxc_snapshots
4,0K rootfs
0 rootfs.dev
0 ccc.log

$ cat /var/lib/lxc/ccc/lxc_snapshots

@brauner do you remember how that logic works?

Hm, this looks like a lxc_snapshots file that didn’t get removed after all clones were deleted. Please remove the file manually and try the destroy again.