diff --git a/beat/backend/python/data.py b/beat/backend/python/data.py
index 572d290a711473f9a9bfb13323dedf6cb6986968..a9f699a7f1526c93f5d3f445f207a78da11054d1 100755
--- a/beat/backend/python/data.py
+++ b/beat/backend/python/data.py
@@ -65,10 +65,10 @@ class RemoteException(Exception):
             self.user_error = message
 
     def __str__(self):
-        if self.system_error != '':
-            return '(sys) ' + self.system_error
+        if self.system_error:
+            return '(sys) {}'.format(self.system_error)
         else:
-            return '(usr) ' + self.user_error
+            return '(usr) {}'.format(self.user_error)
 
 
 #----------------------------------------------------------