[Machines][RFE] There is no hint to show that the results of head is failed when adding disk by "custom path"

Version-Release number of selected components (if applicable):
cockpit-machines-291-1.el9.noarch
cockpit-292-1.el9.x86_64
libvirt-dbus-1.4.1-5.el9.x86_64
libvirt-client-9.3.0-2.el9.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Prepare a shutoff vm, and prepare disk like:
# qemu-img create -f qcow2 /tmp/test_qcow2 10M
# qemu-img create -F qcow2 -b test_qcow2 -f qcow2 /tmp/test_backing_qcow2

2. Create a script like below, then mount it by "mount -o bind ${scriptName} ${headPath}"
"
#!/bin/bash
exit 1
"
Here it is : mount -o bind test.sh /usr/bin/head

3. Click "Add disk",  Input "/tmp/test_backing_qcow2" to the "Custom path" input
There is no hint to show that the results of head is failed


Actual results:
See step3 .


Expected results:
There should be  hint to show that the results of head is failed


Additional info: