Enable HSTS seconds

shimatta_kenkyusho/shimatta_kenkyusho/settings_production.py

@@ -17,6 +17,8 @@ The following environment variables have to be set:
 - DJANGO_MEDIA_ROOT
 - DJANGO_POSTGRESQL_SOCKET
 
+The following can be set
+- DJANGO_SECURE_HSTS_SECONDS (defaults to 120)
 
 """
 
@@ -26,10 +28,12 @@ import os
 # Build paths inside the project like this: BASE_DIR / 'subdir'.
 BASE_DIR = Path(__file__).resolve().parent.parent
 
-def get_env_value(env_variable):
+def get_env_value(env_variable, default=None):
 	try:
 	  	return os.environ[env_variable]
 	except KeyError:
+		if default is not None:
+            return default
         error_msg = 'Set the {} environment variable'.format(env_variable)
 		raise Exception(error_msg)
 
@@ -226,3 +230,5 @@ SESSION_COOKIE_SECURE = True
 CSRF_COOKIE_SECURE = True
 
 SECURE_SSL_REDIRECT = True
+
+SECURE_HSTS_SECONDS = get_env_value('DJANGO_SECURE_HSTS_SECONDS', default=120)