"invalid resource name "docker.io/xxxxx/yyyyy": [may not contain '/']" when doing a hard prune

Issue

Docker registry hard prune fails with the following error:

$ oc -n default exec -i -t docker-registry-32-5vd72 -- /usr/bin/dockerregistry -prune=delete -v 5
WARN[0000] Ignoring unrecognized environment variable REGISTRY_CONSOLE_PORT
WARN[0000] Ignoring unrecognized environment variable REGISTRY_CONSOLE_PORT_9000_TCP
WARN[0000] Ignoring unrecognized environment variable REGISTRY_CONSOLE_PORT_9000_TCP_ADDR
WARN[0000] Ignoring unrecognized environment variable REGISTRY_CONSOLE_PORT_9000_TCP_PORT
WARN[0000] Ignoring unrecognized environment variable REGISTRY_CONSOLE_PORT_9000_TCP_PROTO
WARN[0000] Ignoring unrecognized environment variable REGISTRY_CONSOLE_SERVICE_HOST
WARN[0000] Ignoring unrecognized environment variable REGISTRY_CONSOLE_SERVICE_PORT
WARN[0000] Ignoring unrecognized environment variable REGISTRY_CONSOLE_SERVICE_PORT_REGISTRY_CONSOLE
I1104 19:46:44.179553     226 merged_client_builder.go:123] Using in-cluster configuration
I1104 19:46:44.179992     226 merged_client_builder.go:160] Using in-cluster namespace
I1104 19:48:36.755707     226 request.go:624] Error in request: invalid resource name "docker.io/xxxxx/yyyyy": [may not contain '/']
ERRO[0112] failed to get the image stream isname/docker.io/xxxxx/yyyyy: invalid resource name "docker.io/xxxxx/yyyyy": [may not contain '/']
Deleted 0 blobs
Freed up 0B of disk space
command terminated with exit code 1