Fix qstr in objlist.c; add more tests for list.index.

list.index fails on an edge case.

py/objlist.c

@@ -194,7 +194,7 @@ static mp_obj_t list_index(int n_args, const mp_obj_t *args) {
          }
     }
 
-    nlr_jump(mp_obj_new_exception_msg(rt_q_ValueError, "Object not in list."));
+    nlr_jump(mp_obj_new_exception_msg(MP_QSTR_ValueError, "object not in list"));
 }
 
 static MP_DEFINE_CONST_FUN_OBJ_2(list_append_obj, mp_obj_list_append);

tests/basics/tests/list_index.py

 a = [1, 2, 3]
+print(a.index(1))
+print(a.index(2))
+print(a.index(3))
+print(a.index(3, 2))
+try:
+    print(a.index(3, 2, 2))
+except ValueError:
+    print("Raised ValueError")
+else:
+    print("Did not raise ValueError")
+
 a = a + a
 b = [0, 0, a]
 print(a.index(2))
 print(b.index(a))
 print(a.index(2, 2))
+
 try:
     a.index(2, 2, 2)
 except ValueError:
     print("Raised ValueError")
 else:
-    raise AssertionError("Did not raise ValueError")
+    print("Did not raise ValueError")