完善contest和announcement单元测试

announcement/urls/oj.py

@@ -3,5 +3,5 @@ from django.conf.urls import url
 from ..views.oj import AnnouncementAPI
 
 urlpatterns = [
-    url(r"^announcement/?$", AnnouncementAPI.as_view(), name="announcement_admin_api"),
+    url(r"^announcement/?$", AnnouncementAPI.as_view(), name="announcement_api"),
 ]