Always raise RPCException in RPCExecute

So when calling RPCExecute without processing exception, all exceptions can be
catch with RPCException.

Closes #12874
(grafted from 372dbf53977e872ae62dbc8d6ce5bdc3bcacec69)

--HG--
branch : 7.0

tryton/tryton/common/common.py

@@ -1254,7 +1254,7 @@ class RPCProgress(object):
 
         def return_():
             if self.exception:
-                raise self.exception
+                raise RPCException(self.exception)
             else:
                 return self.res