1. catch ret None issue in rsf.py

2. make param expires optional for GetPolicy in rs/rs_token.py

Author: ZhaoYu

qiniu/rs/rs_token.py

@@ -77,8 +77,8 @@ def token(self, mac=None):
 
 class GetPolicy(object):
 	expires = 3600
-	def __init__(self):
-		pass
+	def __init__(self, expires=3600):
+		self.expires = expires
 
 	def make_request(self, base_url, mac=None):
 		'''

qiniu/rsf.py

@@ -36,6 +36,6 @@ def list_prefix(self, bucket, prefix=None, marker=None, limit=None):
 			ops['prefix'] = prefix
 		url = '%s?%s' % ('/list', urllib.urlencode(ops))
 		ret, err = self.conn.call_with(url, body=None, content_type='application/x-www-form-urlencoded')
-		if not ret.get('marker'):
+		if not ret or not ret.get('marker'):
 			err = EOF
 		return ret, err