Minor nit. Make the rotate() success/fail tests consistent.

Modules/_collectionsmodule.c

@@ -634,7 +634,7 @@ deque_rotate(dequeobject *deque, PyObject *args)
 
     if (!PyArg_ParseTuple(args, "|n:rotate", &n))
         return NULL;
-    if (_deque_rotate(deque, n) == 0)
+    if (!_deque_rotate(deque, n))
         Py_RETURN_NONE;
     return NULL;
 }
@@ -864,7 +864,7 @@ deque_remove(dequeobject *deque, PyObject *value)
         if (cmp > 0) {
             PyObject *tgt = deque_popleft(deque, NULL);
             assert (tgt != NULL);
-            if (_deque_rotate(deque, i) == -1)
+            if (_deque_rotate(deque, i))
                 return NULL;
             Py_DECREF(tgt);
             Py_RETURN_NONE;
@@ -959,7 +959,7 @@ deque_del_item(dequeobject *deque, Py_ssize_t i)
     int rv;
 
     assert (i >= 0 && i < Py_SIZE(deque));
-    if (_deque_rotate(deque, -i) == -1)
+    if (_deque_rotate(deque, -i))
         return -1;
     item = deque_popleft(deque, NULL);
     rv = _deque_rotate(deque, i);