It is bad way to use. Maybe sometimes you can see that way in speaking situation, it must be a kind of joke or so on.

it's a wrong use of 'desu' when you have a verb finished in ~masu/~mashou you can't add desu. desu is an auxiliar so you don't put it after a masu/mashou becouse it's already a complete sentence however you can use in other verbal constructions, ex tabetai desu (i want to eat), but it changes the meaning of the expression as you can see good luck!

Yes, it is bad.

Thanks 4 answering guys!