Mention exception in docstring
diff --git a/Objects/setobject.c b/Objects/setobject.c
index fbbdf6e..075f8e7 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -754,7 +754,8 @@
 	return key;
 }
 
-PyDoc_STRVAR(pop_doc, "Remove and return an arbitrary set element.");
+PyDoc_STRVAR(pop_doc, "Remove and return an arbitrary set element.\n\
+Raises KeyError if the set is empty.");
 
 static int
 set_traverse(PySetObject *so, visitproc visit, void *arg)