promise: Use six instead try...except in check_surykatka_json

slapos/promise/plugin/check_surykatka_json.py

@@ -7,10 +7,7 @@ import email.utils
 import json
 import os
 import time
-try:
-  from urlparse import urlparse
-except ImportError:
-  from urllib.parse import urlparse
+from six.moves.urllib.parse import urlparse
 
 
 @implementer(interface.IPromise)