use secret key file

oj/custom_settings.example.py

@@ -1,2 +0,0 @@
-# please set your own SECRET_KEY to a long random string
-# SECRET_KEY = ""

oj/settings.py

@@ -13,7 +13,6 @@ import os
 import raven
 from copy import deepcopy
 from utils.shortcuts import get_env
-from .custom_settings import *
 
 production_env = get_env("OJ_ENV", "dev") == "production"
 if production_env:
@@ -21,6 +20,9 @@ if production_env:
 else:
     from .dev_settings import *
 
+with open(os.path.join(DATA_DIR, "config", "secret.key"), "r") as f:
+    SECRET_KEY = f.read()
+
 BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 
 # Applications