Custom Images and ISCSI attached Block Volumes

Summary

What are the possible consequences of creating custom image without detaching the ISCSI Block Volumes

Content

What are the possible consequences of creating custom image without detaching the ISCSI Block Volumes 

Is it when you create the image  or if you try to boot from the image ? 

The warning for this is easily missed,

Could not the console check before allowing a create custom image ?   (along with not allowing a compute instance launch without a ssh key) 

Thanks
Dominic