virt-v2v failed to convert KVM guests images with error "No operating system could be detected inside this disk image"

Issue

When trying to convert an existing KVM guest with virt-v2v to import it in RHEV  fails with this message:

find: failed to restore initial working directory: Permission denied

No operating system could be detected inside this disk image.

This may be because the file is not a disk image, or is not a virtual machine
image, or because the OS type is not understood by virt-inspector.

If you feel this is an error, please file a bug report including as much
information about the disk image as possible.