Index: Lib/xmlrpclib.py
===================================================================
--- Lib/xmlrpclib.py	(revision 77393)
+++ Lib/xmlrpclib.py	(working copy)
@@ -257,6 +257,28 @@
     """Indicates a broken response package."""
     pass
 
+
+class MarshallError(Error):
+    """Indicates an error occured while marshalling to/from XML"""
+    def __init__(self, message, value, key=None, slot=None):
+        self.message = message
+        self.value = value
+        self.slot = slot
+        self.key = key
+
+    def __repr__(self):
+        message = str(self.message)
+
+        if self.slot is not None:
+            message += "; slot %s" % self.slot
+
+        if self.key is not None:
+            message += "; key %s" % self.key
+
+        message += "; value='%s'" % self.value
+
+        return "<marshallerror> %s </marshallerror>" % message
+
 ##
 # Indicates an XML-RPC fault response package.  This exception is
 # raised by the unmarshalling layer, if the XML-RPC response contains
@@ -608,17 +630,24 @@
 
     dispatch = {}
 
+    def dump_fault(self, fault, write, dump):
+        '''dumps the fault provided to the writer'''
+        self._dump_fault(fault.faultCode, fault.faultString, write, dump)
+
+    def _dump_fault(self, faultCode, faultString, write, dump):
+        '''dumps the fault code and string to the writer provided'''
+        write("<fault>\n")
+        dump({'faultCode': faultCode,
+              'faultString': faultString},
+             write)
+        write("</fault>\n")
+
     def dumps(self, values):
         out = []
         write = out.append
         dump = self.__dump
         if isinstance(values, Fault):
-            # fault instance
-            write("<fault>\n")
-            dump({'faultCode': values.faultCode,
-                  'faultString': values.faultString},
-                 write)
-            write("</fault>\n")
+            self.dump_fault(values, write, dump)
         else:
             # parameter block
             # FIXME: the xml-rpc specification allows us to leave out
@@ -626,12 +655,27 @@
             # however, changing this may break older code (including
             # old versions of xmlrpclib.py), so this is better left as
             # is for now.  See @XMLRPC3 for more information. /F
-            write("<params>\n")
-            for v in values:
-                write("<param>\n")
-                dump(v, write)
-                write("</param>\n")
-            write("</params>\n")
+            try:
+                params = []
+                write = params.append
+
+                write("<params>\n")
+                for pos, v in enumerate(values):
+                    write("<param>\n")
+                    dump(v, write)
+                    write("</param>\n")
+                write("</params>\n")
+
+                out.extend(params)
+            except MarshallError, e:
+                fault = []
+                write = fault.append
+                message = "could not serialize value #%d: %s" % (pos,
+                                                                 str(e))
+                self._dump_fault(8002, message, write, dump)
+
+                out.extend(fault)
+
         result = string.join(out, "")
         return result
 
@@ -710,8 +754,12 @@
         self.memo[i] = None
         dump = self.__dump
         write("<value><array><data>\n")
-        for v in value:
-            dump(v, write)
+        for pos, v in enumerate(value):
+            try:
+                dump(v, write)
+            except Exception, e:
+                raise MarshallError(e, v, slot=pos)
+
         write("</data></array></value>\n")
         del self.memo[i]
     dispatch[TupleType] = dump_array
@@ -732,7 +780,11 @@
                 else:
                     raise TypeError, "dictionary key must be string"
             write("<name>%s</name>\n" % escape(k))
-            dump(v, write)
+            try:
+                dump(v, write)
+            except Exception, e:
+                raise MarshallError(e, v, key=k)
+
             write("</member>\n")
         write("</struct></value>\n")
         del self.memo[i]