On creating a VM from template, and selecting the disk to be container disk:

VM > from template > fedora vm > disk source > registry

In case the tag has spaces the pod fail to start with the following error
 
Error creating DataVolume fedora-emerald-fowl-53: admission webhook "datavolume-validate.cdi.kubevirt.io" denied the request: Illegal registry source URL docker:// quay.io/kubevirt/fedora-with-test-tooling-container-disk:v1.5.1
 
The issure reproduce for following inputs that includes spaces at the start or end of the image tag, for exmaple:
"    quay.io/kubevirt/fedora-with-test-tooling-container-disk:v1.5.1"
" quay.io/kubevirt/fedora-with-test-tooling-container-disk:v1.5.1     "