Update README.rst

README.rst

@@ -79,7 +79,7 @@ Use ``@overrides`` to indicate that a subclass method should override a supercla
             return y
             
         @overrides
-        def zoo(self): # Raises, because does not exists in the super class.
+        def zoo(self): # Raises, because does not exist in the super class.
             return "foobarzoo"
 
 Use ``EnforceOverrides`` to require subclass methods that shadow superclass methods to be decorated