Hi there, I staged a house once for a lovely Indian couple whose home smelled of curry.  It is a very touchy subject to talk about with the homeowners because you don't want to insult them, but it is an issue that needs to be dealt with in order to sell the home.  I would politely say to them that when you have lived in your home for a while, you become accustom to the smells of the home.  That you noticed in one of the bedrooms, you could really smell the pet odor and this is something that could turn buyers away.  I have been told this product works amazing.  I've not tried it yet myself, but several people I know have used it and swear by it.  Here is the website.  www.fresh-wave.com

Good luck.  Let us know how things work out for you.