Add new function and fix a bug.

* SearpcError.msg should be a string object.

lib/rpc_table.py

@@ -41,4 +41,5 @@ func_table = [
     [ "object", [] ],
     [ "object", ["int"] ],
     [ "object", ["string"] ],
+    [ "object", ["string", "string"] ],
 ]

pysearpc/client.py

@@ -81,7 +81,7 @@ def searpc_func(ret_type, param_types):
                 try:
                     return fret(ret_str)
                 except fcallfret.error, e:
-                    raise SearpcError(e)
+                    raise SearpcError(str(e))
 
         def newfunc_obj(self, *args):
             fcall_str = fcall(func.__name__, *args)