I dont know the details of your coop. I do know that "no pet clauses" are not enforceable in Ontario. Clearly local by-laws will still apply, but it may be the case that they have no legal right to force you to sell. May not be worth the fight, but if you feel strongly, you could get a legal opinion from a lawyer.
NOTE: I am most certainly NOT a lawyer. My opinion is just that...an opinion.
1 adult bull snake: "Dozer"; 1.1 juvenile bull snakes: Oscar and Phoebe; 3 baby red-sided garters; 1.1 macklot's pythons