On errors MTV does not specify what the error is. For example after migrating a VM with a RHEV user with restricted permissions the migration pod has the following at the end:

I0225 17:13:18.302219 1 prometheus.go:69] 100.00
I0225 17:13:19.302730 1 prometheus.go:69] 100.00
I0225 17:13:20.198131 1 data-processor.go:231] New phase: Resize
I0225 17:13:20.199448 1 data-processor.go:231] New phase: Complete
I0225 17:13:20.199597 1 importer.go:217] Import Complete
E0225 17:13:20.224397 1 imageio-datasource.go:155] Unable to finalize or cancel transfer! Disk may remain locked until inactivity timeout.
Fault reason is "Operation Failed". Fault detail is "[User is not authorized to perform this action.]". HTTP response code is "403". HTTP response message is "403 Forbidden".
Fault reason is "Operation Failed". Fault detail is "[User is not authorized to perform this action.]". HTTP response code is "403". HTTP response message is "403 Forbidden".

What exactly is the problem? Which action failed? It's impossible to debug without detailed information.