[cups] Cannot disable low ink warning

[R. Diez]

Hallo all:

Every time I print, I get a low ink warning in the form of a desktop 
notification. More info is here:

https://bugs.launchpad.net/ubuntu/+source/hplip/+bug/305609

However, my printer is not an HP, but a Sharp MX-4100N.

The troubleshooter says:
   Status Messages

   There are status messages associated with this queue.

   The printer's state message is: 'Waiting for printer to finish.'.

   Warnings are listed below:
   Printer 'Sharp-MX-4100N" has no toner left.

The "waiting" status is also weird. The print job is empty.

I am told that the printer has toner. I am not the sysadmin. I have no 
control over the printer. Printing from Windows is fine. I am only 
getting this warning since a few days ago, and as far as I know, nothing 
has been changed on the printer. Printing is fine, by the way, it's only 
the annoying warning.

By the way, I selected driver "PCL 6/PCL XL Printer - CUPS+Gutenprint 
v5.2.10-pre2 (en)". I do not really know much about CUPS, I am just a 
user who wants to print. 8-)

I am using Ubuntu 16.04.2, but I suspect that this is a generic CUPS 
issue. Is there a way to disable that kind of pop-up warning completely?

Thanks in advance,
   rdiez