This is the patch required for ZSI to return error codes properly, 
You can track the version I submitted here:
https://sourceforge.net/tracker/?func=detail&atid=387667&aid=1697819&group_id=26590
David Fraser <davidf@sjsoft.com>
2007-05-03

--- ZSI/dispatch.py	2007-01-26 22:01:10.000000000 +0200
+++ ZSI/dispatch.py	2007-04-10 18:36:43.220125000 +0200
@@ -73,8 +73,7 @@
             try:
                 arg = tc.parse(ps.body_root, ps)
             except EvaluateException, ex:
-                SendFault(FaultFromZSIException(ex), **kw)
-                return
+                return SendFault(FaultFromZSIException(ex), **kw)
 
             try:
                 result = handler(arg)
@@ -97,8 +96,7 @@
                 try:
                     kwargs[str(e.localName)] = tc.parse(e, ps)
                 except EvaluateException, ex:
-                    SendFault(FaultFromZSIException(ex), **kw)
-                    return
+                    return SendFault(FaultFromZSIException(ex), **kw)
 
             result = handler(**kwargs)
             aslist = False
@@ -125,15 +123,13 @@
                 try: arg = [ tc.parse(e, ps) for e in data ]
                 except EvaluateException, e:
                     #SendFault(FaultFromZSIException(e), **kw)
-                    SendFault(RuntimeError("THIS IS AN ARRAY: %s" %isarray))
-                    return
+                    return SendFault(RuntimeError("THIS IS AN ARRAY: %s" %isarray))
 
                 result = handler(*arg)
             else:
                 try: kwarg = dict([ (str(e.localName),tc.parse(e, ps)) for e in data ])
                 except EvaluateException, e:
-                    SendFault(FaultFromZSIException(e), **kw)
-                    return
+                    return SendFault(FaultFromZSIException(e), **kw)
 
                 result = handler(**kwarg)