The std::cout and qDebugs on the external command helper is
not visible to the user as it runs in another process via dbus
this is highly annoying if you want to be able to discover what's
wrong on the command line.
A method that checks if the file is in the right place should be
called by the users of this library
The previous way relied on kernel device numbers but this gets ugly, especially
in cases when device number is not assigned such as virtio disks.
BUG: 378607