Handle SimpleXMLRPCDispatcher arg count change in Py2.5

SimpleXMLRPCDispatcher.__init__ takes 3 arguments instead of 1 since
python 2.5, so we check for that with a hack, for I found no better way,
other than catching a TypeError exception.

Signed-off-by: martin f. krafft <madduck@madduck.net>

doc/bugs/rst_plugin_traceback_with_SimpleXMLRPCDispatcher_from_pyhton_2.5.mdwn

@@ -9,3 +9,5 @@ After adding rst to plugins, ikiwiki --setup fails:
 
 This is ikiwiki version 2.40 and
 [SimpleXMLRPCServer.py](http://svn.python.org/view/python/tags/r25/Lib/SimpleXMLRPCServer.py?rev=51918&view=markup) from python-2.5
+
+[[done]]

plugins/rst

@@ -61,8 +61,12 @@ def rpc_call(cmd, **kwargs):
 
 class SimpleStdinOutXMLRPCHandler(SimpleXMLRPCDispatcher):
 
-    def __init__(self):
+    def __init__(self, allow_none=False, encoding=None):
+        if SimpleXMLRPCDispatcher.__init__.func_code.co_argcount == 1:
+            # python2.4 and before only took one argument
             SimpleXMLRPCDispatcher.__init__(self)
+        else:
+            SimpleXMLRPCDispatcher.__init__(self, allow_none, encoding)
 
     def process_request(self, req):
         write(self._marshaled_dispatch(req))