Best practice is to use the 'hmp_handle_error' function, not
'monitor_printf' or 'error_report_err'. This ensures that the
message always gets an 'Error: ' prefix, distinguishing it
from normal command output.
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>